Zero-Day Exploit: Risks, Famous Examples, Trends & Mitigations

What Is a Zero-Day Exploit? 

A zero-day exploit is a cyberattack that uses an unknown software vulnerability before the developer has a chance to fix it. Because the software vendor has had "zero days" to patch the vulnerability, users are left exposed to attacks that can lead to data breaches, financial loss, and other serious consequences.

Zero-day exploits are especially dangerous because they are unknown to defenders. Because the vulnerability is unknown to the software vendor, there are no patches or defenses available to protect against it.  The "zero-day window," the time between the exploit's discovery and its patching, can last for weeks, months, or even years. Successful zero-day attacks can lead to major data breaches, financial theft, and disruption of services.

The zero day vulnerability process involves the following stages:

1. Vulnerability discovery: A developer or hacker finds a flaw in a piece of software, operating system, or hardware. 
2. Exploit development: The discoverer creates a piece of code, or "exploit," to take advantage of this vulnerability. 
3. Exploitation: The attacker uses the exploit to attack systems, either before or shortly after the vulnerability is publicly known. 
4. Patching: The software vendor, once aware of the flaw, develops and releases a patch to fix the vulnerability. Once the patch is released, the exploit is no longer considered a "zero-day".

Famous examples of zero-day attacks include:

• Pegasus Spyware (Ongoing): Developed by the NSO Group, this spyware has repeatedly leveraged "zero-click" zero-day vulnerabilities in apps like iMessage and WhatsApp to remotely compromise targets' devices.
• MOVEit transfer (2023): The CLOP ransomware gang exploited a zero-day SQL injection vulnerability in the Progress Software MOVEit Transfer product to steal data from numerous organizations.
• Zoom vulnerability (2020): Attackers could gain remote access to user computers through a zero-day flaw in the video conferencing software. 

Zero-day exploits are highly sought after by hackers, cybercriminal groups, and adversaries because of their unpredictability. Once details about the vulnerability become public or a patch is released, the window of opportunity for attackers narrows considerably.

This is part of a series of articles about zero day attacks.

The Security Risks of Zero-Day Exploits

Zero-day exploits introduce a set of challenges for defenders because they strike without warning and often bypass conventional security controls. Their unpredictable nature and high impact make them one of the most dangerous threats in cybersecurity.

• No available patch or fix: Since the vulnerability is unknown to the vendor at the time of exploitation, there is no immediate remedy or patch. This leaves systems exposed until a fix is developed and deployed.
• Bypass of traditional security tools: Zero-day attacks often go undetected by antivirus, intrusion detection systems, and endpoint protection platforms, which rely on known threat signatures or behaviors.
• Rapid exploitation and spread: Attackers can exploit zero-day flaws quickly and on a wide scale, often automating their attacks to compromise many systems before defenders respond.
• High value for attackers: Nation-state actors and cybercriminals invest heavily in discovering or purchasing zero-day exploits due to their strategic advantages, especially in espionage, sabotage, or large-scale cybercrime
• Difficult attribution: Because zero-day exploits leave little initial evidence and often resemble legitimate activity, tracing the origin or intent of the attack can be complex and time-consuming.
• Potential for long-term undetected access: Attackers using zero-day exploits can maintain persistence within a system for extended periods, exfiltrating data or preparing additional attacks before being discovered.
• Increased damage potential: The lack of preparedness and effective defenses at the time of a zero-day exploit increases the potential impact, including data breaches, operational disruption, and financial losses.

Types of Zero-Day Exploits 

Software and OS Exploits

Software and operating system (OS) zero-day exploits target undiscovered vulnerabilities in widely used applications or system-level software. These may include flaws in code execution, memory management, or privilege escalation paths that allow attackers to run malicious code, take administrative control, or bypass user authentication entirely. Common targets include popular office suites, email clients, database software, and components of operating systems.

Attackers value software and OS zero-days because of their ubiquity and potential for large-scale compromise. For example, a single zero-day in a widely deployed platform like Windows or Linux can provide attackers with access to millions of endpoints. System administrators face particular challenges defending against these threats due to the sheer scale and diversity of software environments.

Hardware and Firmware Zero-Days

Hardware and firmware zero-day vulnerabilities impact underlying device functionality, such as BIOS, embedded controllers, or processors. These exploits are especially dangerous because they can compromise the foundational operations of a system, remain persistent across software reinstalls, and evade most traditional security measures. 

Attackers may leverage flaws in device firmware to achieve long-term stealth, manipulate hardware behavior, or create “hardware backdoors” that provide covert access even after apparent remediation of software issues. Defending against hardware and firmware zero-days is challenging due to limited visibility and the specialized nature of patching embedded or low-level system components. 

Supply-Chain Zero-Day Vulnerabilities

Supply-chain zero-day exploits take advantage of vulnerabilities that are introduced during the manufacturing, distribution, or update processes for hardware and software. These flaws can be embedded in compromised components, malicious updates, or third-party libraries that are consumed by software vendors and integrated into trusted products. 

Attackers using supply-chain zero-days can gain privileged access to targeted environments indirectly, which makes detection and attribution far more complex and the attack surface substantially larger. A breach in one supplier can propagate to thousands of downstream customers, as seen in high-profile incidents like the SolarWinds compromise. 

Browser and Application Zero-Days

Browser and application zero-day exploits are among the most rapidly weaponized because of browsers’ pervasive use as gateways to the internet. Vulnerabilities in major web browsers, such as Chrome, Firefox, Safari, or Edge, can allow attackers to execute arbitrary code, steal user credentials, or bypass security sandboxes with little user interaction. 

Additionally, popular productivity or media applications are frequent targets, as exploit kits can distribute malware through document, PDF, or video file vulnerabilities. These exploits are often delivered through drive-by downloads, phishing attacks, or malicious advertisements. The constantly evolving browser landscape and heavy reliance on third-party plugins compound the risk. 

Famous Examples of Zero Day Exploits 

Pegasus Spyware (Ongoing)

Pegasus is a mobile surveillance tool developed by the NSO Group, originally intended for government use but widely misused to spy on journalists, activists, and political figures. Its core strength lies in its ability to exploit zero-day vulnerabilities, many of which require no user interaction. 

These “zero-click” attacks can be delivered through vectors like iMessage, FaceTime, or WhatsApp, silently compromising both iOS and Android devices. Once installed, Pegasus can access messages, call logs, passwords, GPS data, and even activate microphones and cameras without alerting the user.

Detection is difficult because Pegasus is engineered for stealth, employing techniques like code obfuscation, encrypted data exfiltration, and a self-destruct mechanism that removes traces if exposure is likely. Traditional antivirus tools often fail to detect it. Researchers rely on encrypted device backups and forensic tools like the Mobile Verification Toolkit (MVT) to identify infections. 

MOVEit Transfer (2023)

In May 2023, a zero-day SQL injection vulnerability (CVE-2023-34362) in MOVEit Transfer was actively exploited by the CL0P ransomware group. The attackers used the flaw to deploy a custom web shell named LEMURLOOT on internet-facing servers, enabling persistent access and data exfiltration. 

Disguised to resemble legitimate MOVEit components and protected by hidden credentials, the shell allowed CL0P to evade detection while harvesting sensitive files across numerous organizations. The breach affected thousands of vulnerable MOVEit servers globally, as no patch was available at the time of the initial attacks. 

Exploitation attempts began on May 27, days before the vendor's public advisory. Investigators later confirmed that attackers used obfuscated request headers and concealed shell access points to avoid standard discovery methods. Security vendors blocked several attack attempts using anomaly detection and behavioral analysis, but the scope of impacted victims remains significant.

Zoom Vulnerability (2020)

During the early months of the COVID-19 pandemic, Zoom experienced a major surge in usage, alongside a series of security issues. One critical vulnerability stemmed from how the Zoom Windows client handled UNC paths in group chats, automatically converting them into clickable links. 

This flaw allowed attackers to exfiltrate Windows credentials when unsuspecting users clicked the links. Compounded by poor meeting security defaults, attackers could guess or reuse meeting IDs, leading to unauthorized access and data leaks. The breach compromised over 500 million user credentials and exposed sensitive information, including government discussions. 

Notably, UK Prime Minister Boris Johnson accidentally revealed his permanent meeting ID in a public screenshot, highlighting the risks of poor security practices. In response, Zoom implemented preventative and corrective controls, such as single-use meeting IDs, password-protected sessions, and tighter access roles.

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Who Develops and Uses Zero-Day Exploits? 

State-Sponsored Actors

State-sponsored actors are heavily invested in finding and leveraging zero-day exploits for cyber espionage, sabotage, and geopolitical influence. These groups, often linked to intelligence agencies or military units, possess significant financial and technical resources to discover new vulnerabilities or purchase them from external brokers. 

The actions of state-sponsored actors raise global cyber conflict concerns, as their operations blur the line between espionage and cyberwarfare. Attribution can also be challenging, as advanced persistent threat (APT) groups take extreme measures to obfuscate their origins and intentions. 

Cybercriminal Groups and APTs

Cybercriminal groups and advanced persistent threats (APTs) are aggressive consumers and developers of zero-day exploits. These actors target organizations for profit or long-term espionage, using zero-days in ransomware campaigns, financial fraud operations, or intellectual property theft. Cybercriminals are primarily motivated by financial gain. They often monetize exploits quickly, using them in widespread campaigns or selling access to other threat groups.

APTs, while sometimes state-affiliated, operate with a focus on sustained access and data gathering. Both cybercriminals and APTs invest in discovering new vulnerabilities, leveraging zero-days to compromise targeted entities before detection or remediation. 

Security Researchers and Ethical Hackers

Security researchers and ethical hackers aid in the discovery and disclosure of zero-day vulnerabilities. Operating with the intention of improving system security, these individuals or teams identify flaws using both automated tools and manual analysis. Upon discovery, most responsible researchers report their findings directly to vendors or participate in bug bounty programs that reward the timely identification of vulnerabilities. 

Despite good intentions, the efforts of security researchers are not without controversy. Some researchers may publish exploit details if responsible disclosure agreements fail, potentially enabling attackers. Others debate where to draw the line between responsible reporting and publicizing vulnerabilities for recognition or financial reward. 

Brokers and Gray-Market Exploit Dealers

Brokers and gray-market exploit dealers form a clandestine marketplace for zero-day vulnerabilities. These intermediaries connect sellers, often individual researchers or hackers, with buyers who may be governments, corporations, or organized cybercriminals. Zero-day exploits can fetch extremely high prices on the gray market, particularly if they offer remote code execution or privilege escalation capabilities in widely-used software. 

These dealers operate in secrecy, leveraging encrypted communication platforms and requiring rigorous vetting of potential clients to avoid law enforcement or rival actors. This marketplace perpetuates the existence of zero-day threats, as incentives to sell to the highest bidder can outweigh ethical considerations. 

Emerging Trends in Zero-Day Exploits 

Zero-Day Use in AI-Driven Cyberwarfare

Artificial intelligence is transforming how zero-day exploits are discovered, weaponized, and deployed in cyberwarfare. AI-powered tools can automate vulnerability scanning, analyze massive codebases for hidden flaws, and generate exploit prototypes more efficiently than human researchers. Adversarial AI systems can also be trained to adapt exploit techniques in real time, evading signature-based detection.

This increased automation is enabling state actors, cybercriminals, and large APT groups to accelerate their offensive capabilities. The use of AI in zero-day operations reduces the window for defenders to detect, analyze, and respond to novel threats. As machine learning models improve, the ability to identify and exploit zero-day vulnerabilities will likely become more widespread.

The Role of Deepfake and LLMs in Exploit Delivery

Deepfake technology and large language models (LLMs) are being incorporated into zero-day exploit campaigns to enhance deception, spear-phishing, and social engineering. Using deepfakes, attackers can convincingly impersonate trusted contacts, executives, or support technicians, increasing the likelihood that targets will interact with malicious content or divulge sensitive information. 

LLMs can generate natural-sounding phishing emails or create dynamic, personalized lures that better evade anti-spam filters. When used in conjunction with zero-day exploits, these technologies boost attackers’ ability to deliver payloads and compromise systems without detection. Defenders must now contend with both technical vulnerabilities and highly believable human-like interactions crafted by AI tools. 

Quantum-Safe Defense Considerations

The advent of quantum computing threatens to undermine traditional cryptographic protections that organizations rely on to defend against zero-day exploits and related lateral movement. Quantum-capable attackers could theoretically break encryption used in software updates, secure messaging, and system authentication, opening new avenues for exploit delivery or escalation. 

This has spurred the development and gradual adoption of quantum-safe cryptographic algorithms designed to remain resistant to both classical and quantum attacks. In parallel, security professionals are reevaluating internal trust boundaries and incident response processes to anticipate a post-quantum threat environment. 

The Rise of Exploit-as-a-Service Ecosystems

Exploit-as-a-service (EaaS) has emerged as an organized business model where cybercriminal networks rent access to zero-day exploits and attack infrastructure on demand. These services lower the barrier to entry for less sophisticated attackers, who can deploy advanced attacks without direct vulnerability research or exploit development expertise. 

EaaS providers often offer everything from step-by-step deployment guides to automated exploit delivery platforms and customer support, mimicking legitimate SaaS models. The EaaS model accelerates the proliferation of zero-day attacks by democratizing access. Defenders now face the challenge of rapidly evolving threat actors who can launch coordinated attacks at scale. 

Preventing and Mitigating Zero-Day Exploits 

Here are some of the ways that organizations can protect themselves from zero-day attacks.

1. Utilize Cloud Application Detection & Response (CADR) Solutions

Cloud Application Detection & Response (CADR) solutions focus on monitoring the behavior of applications and systems as they operate, rather than relying solely on signature-based detection methods. By establishing baselines for activity and scrutinizing deviations, CADR tools can identify the techniques used in zero-day exploits, such as code injection, privilege escalation, or lateral movement, even when no prior indicators exist. 

Deployment of CADR solutions complements traditional preventive controls by catching active exploits in real time. System administrators can use these insights to orchestrate automated containment measures, triggering process isolation, privilege demotion, or network segmentation in response to suspicious behavior. 

Learn more in our detailed guide to runtime security

2. Network Segmentation and Access Control

Network segmentation divides an organization’s infrastructure into smaller, isolated units, limiting lateral movement during a zero-day attack. By enforcing strict internal boundaries and access controls, organizations can contain outbreaks, restrict compromised users’ privileges, and minimize the overall impact of a breach. 

Segmentation is typically achieved using VLANs, software-defined networking, or dedicated firewalls that segment sensitive environments from general user traffic or public-facing services. Complementary to segmentation, granular access control policies, such as least privilege and just-in-time access, reduce the chance that attackers will exploit zero-day vulnerabilities to escalate privileges or move horizontally across networks. 

3. Endpoint Protection and Threat Hunting

Modern endpoint protection platforms employ advanced behavioral analysis, machine learning, and exploit mitigation technologies to identify and block zero-day attacks on individual devices. Unlike traditional antivirus solutions that depend on known signatures, these platforms scrutinize process behaviors, system calls, and memory usage to flag suspicious activity. 

Techniques like exploit prevention, application whitelisting, and rollback of malicious changes add extra layers of defense at the endpoint. Proactive threat hunting teams sift through endpoint telemetry and external threat intelligence to uncover indicators of compromise that standard tools might miss. 

4. Zero Trust Architectures

Zero trust security frameworks operate on the assumption that no user, device, or network segment should be inherently trusted, regardless of its location or origin. Every access request, API call, or data exchange is subject to rigorous authentication, authorization, and continuous verification. 

This “never trust, always verify” philosophy directly constrains the impact of zero-day exploits, as attackers who breach an initial boundary must continually prove legitimacy to move or act within the environment. Transitions to zero trust require architectural changes, investments in identity and access management (IAM), micro-segmentation, and real-time monitoring. These make it harder for zero-day exploits to grant persistent access.

5. Real-Time Exploit Mitigation Systems

Real-time exploit mitigation systems are designed to automatically detect, block, or neutralize zero-day attacks as they happen. These solutions use techniques like in-memory exploit prevention, control flow integrity checks, and sandboxed execution environments to monitor software behavior for exploit signs. When suspicious activity is detected, such as an abnormal system call or memory manipulation, the mitigation system can terminate the offending process.

Real-time mitigation can reduce the attack window for zero-day exploits from hours or days to seconds. Integration with centralized security information and event management (SIEM) systems enables rapid alerting, incident orchestration, and escalation to threat response teams. 

Protecting Against Zero Day Exploits with Oligo

Oligo protects against zero-day exploits by monitoring behavior at runtime across both application code and the underlying cloud infrastructure and workloads—without relying on known CVEs or signatures. By understanding how code, libraries, processes, and cloud workloads actually behave in production, Oligo detects and blocks exploit attempts at the earliest stage of the kill chain, even when the vulnerability is brand new. This runtime-first approach stops zero-days before attackers gain a foothold, without disrupting performance or the business.

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