What Are Known Exploited Vulnerabilities?

Hackers typically use working exploits. That’s why known exploited vulnerabilities sit at the top of every serious IT team’s priority list. They give attackers proven, easy paths into your systems, so ignoring them can lead straight to disaster.

Known Exploited Vulnerabilities (KEVs) Defined

Known exploited vulnerabilities are software or hardware flaws that are not only publicly disclosed but are also confirmed to be actively exploited by cyber threat actors. This means attackers are using these vulnerabilities in real-world attacks, targeting organizations before they have had a chance to patch or mitigate them.

Government agencies and security organizations, such as CISA (the Cybersecurity and Infrastructure Security Agency), maintain public catalogs of these vulnerabilities to help companies speed up mitigation efforts.

Why Do Known Exploited Vulnerabilities Matter?

• Increased Risk: KEVs represent vulnerabilities with a proven, current threat, since attackers are actively exploiting them.
• Patch Prioritization: Focusing on KEVs allows IT and security teams to address the most urgent and impactful risks first, maximizing risk reduction with limited resources.
• Compliance: Many regulatory standards and industry guidelines now require organizations to address known exploited vulnerabilities on a defined timeline.
• Incident Prevention: Remediating KEVs significantly reduces the likelihood of serious breaches stemming from well-known exploits.

Why Do Attackers Target KEVs?

By zeroing in on KEVs, hackers hit targets with techniques they already know will succeed.

• Reliable Success: If attackers use a vulnerability, it works—and it often works fast.
• Wide Impact: KEVs usually affect many companies or popular products, promising big payoffs for criminals.
• Lagging Defenses: Attackers follow the path of least resistance by weaponizing KEVs, knowing the common corporate struggle to patch everything guarantees they will find an easy target. 

How Are KEVs Identified?

Known exploited vulnerabilities are discovered through:

• Threat intelligence feeds and incident reports from cybersecurity researchers
• Government advisories (e.g., CISA KEV Catalog)
• Vendor security bulletins
• Real-world evidence of exploitation (malware samples, attack campaigns, forensics)

Once validated as being actively exploited, these vulnerabilities are added to official KEV lists, which are regularly updated.

Examples of Known Exploited Vulnerabilities

Here are a few KEVs that made serious waves:

• Log4Shell (CVE-2021-44228): Attackers pounced on this quickly, using it to breach networks across industries.
• Microsoft Exchange Hafnium Attacks (2021): Hackers exploited these flaws to break into thousands of companies.
• MOVEit File Transfer Flaw (2023): Ransomware gangs targeted critical data transfers through this vulnerability.
• VPN Issues in Fortinet and Pulse Connect Secure: Healthcare, government, and big businesses suffered hits when hackers took advantage of these weaknesses.

These incidents prove one thing: when hackers spot an open door, they rush in.

How to Respond to Known Exploited Vulnerabilities

• Monitor Official KEV Lists: Regularly review authoritative resources (e.g., CISA KEV Catalog).
• Assess Exposure: Identify affected assets within your environment. Include third-party and legacy systems.
• Mitigate Promptly: Deploy compensating controls to shield critical vulnerabilities. Solutions such as OTTOGUARD.AI provide immediate mitigation, making vulnerabilities unexploitable at runtime, even before you patch.
• Apply Patches Where Possible: Once you secure your environment with mitigation, roll out official patches and permanent fixes as soon as they become available and practical for your systems.

Verify Remediation: Ensure patches or mitigations are applied successfully and validate with vulnerability scans or runtime protection solutions.

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