How severe is CVE-2021-45046?

CVE-2021-45046 has a CVSS score of 9/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-45046?

Affected package information for CVE-2021-45046 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2021-45046?

No fixed version has been published for CVE-2021-45046 yet. Monitor the advisory for updates, apply mitigations recommended by the vendor, and use O3 Security to track when a fix becomes available in your stack.

Is CVE-2021-45046 actively exploited in the wild?

Yes. There are 13 known exploit references for CVE-2021-45046, including 8 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-45046?

CVE-2021-45046 has an EPSS (Exploit Prediction Scoring System) score of 94.3%, placing it in the 100th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

Is CVE-2021-45046 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2021-45046 (Apache Log4j2 Deserialization of Untrusted Data Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2023-05-01. CISA required all US federal civilian agencies to remediate this vulnerability by 2023-05-22. The required action was: Apply updates per vendor instructions. This CVE has been used in known ransomware campaigns. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

CISA KEV·Added 2023-05-01 — agencies required to remediate by 2023-05-22 · Ransomware

CVE-2021-45046

Q: Can O3 Security detect CVE-2021-45046 in my codebase?

Yes. O3 Security's Impact-Aware SCA scanner identifies CVE-2021-45046 across all affected ecosystems (multiple ecosystems), correlates it against your dependency graph, and uses function-level reachability to confirm whether the vulnerable code path is actually reachable in your application — eliminating false positives. You can scan your stack for CVE-2021-45046 directly from the O3 platform.

CRITICAL

Also known asGHSA-7rjr-3q55-vv33

Published

Dec 14, 2021

Updated

Apr 16, 2026

Affected

0 pkgs

Patched

None yet

Exploits

13 known

EPSS Exploitation Probability

via FIRST.org ↗

94.3%probability of exploitation in next 30 days

Very High Risk100th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Description

It was found that the fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete in certain non-default configurations. This could allows attackers with control over Thread Context Map (MDC) input data when the logging configuration uses a non-default Pattern Layout with either a Context Lookup (for example, $${ctx:loginId}) or a Thread Context Map pattern (%X, %mdc, or %MDC) to craft malicious input data using a JNDI Lookup pattern resulting in an information leak and remote code execution in some environments and local code execution in all environments. Log4j 2.16.0 (Java 8) and 2.12.2 (Java 7) fix this issue by removing support for message lookup patterns and disabling JNDI functionality by default.

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.