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?

CVE-2021-45046 affects the following packages: org.apache.logging.log4j:log4j-core (Maven), org.apache.logging.log4j:log4j-core (Maven), org.ops4j.pax.logging:pax-logging-log4j2 (Maven), org.ops4j.pax.logging:pax-logging-log4j2 (Maven), org.ops4j.pax.logging:pax-logging-log4j2 (Maven), org.ops4j.pax.logging:pax-logging-log4j2 (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-45046?

Update org.apache.logging.log4j:log4j-core to 2.16.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-45046 is resolved across your whole dependency graph.

How do I detect CVE-2021-45046 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.logging.log4j:log4j-core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2021-45046 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2021-45046?

O3 pinpoints whether CVE-2021-45046 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

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 100.0%, 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.

What type of vulnerability is CVE-2021-45046?

CVE-2021-45046 is classified as Expression Language Injection (CWE-917). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

Is there exploit tooling available for CVE-2021-45046?

A Nuclei detection template exists for CVE-2021-45046, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2021-45046 published, and has it been updated?

CVE-2021-45046 was published on December 14, 2021 and was last updated on July 8, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

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

☕ Maven

CVE-2021-45046

CRITICAL

Incomplete fix for Apache Log4j vulnerability

Also known asGHSA-7rjr-3q55-vv33

Published

Dec 14, 2021

Updated

Jul 8, 2026

Affected

6 pkgs

Patched

6 / 6

Exploits

13 known

EPSS Exploitation Probability

via FIRST.org ↗

100.0%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.

Blast Radius

6 pkgs affected

☕org.apache.logging.log4j:log4j-core☕org.apache.logging.log4j:log4j-core☕org.ops4j.pax.logging:pax-logging-log4j2☕org.ops4j.pax.logging:pax-logging-log4j2☕org.ops4j.pax.logging:pax-logging-log4j2☕org.ops4j.pax.logging:pax-logging-log4j2

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

6 total 6 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.apache.logging.log4j:log4j-core`	≥ 2.13.0&&< 2.16.0	2.16.0
☕Maven	`org.apache.logging.log4j:log4j-core`	all versions	2.12.2
☕Maven	`org.ops4j.pax.logging:pax-logging-log4j2`	≥ 1.8.0&&< 1.9.2	1.9.2
☕Maven	`org.ops4j.pax.logging:pax-logging-log4j2`	≥ 1.10.0&&< 1.10.8	1.10.8
☕Maven	`org.ops4j.pax.logging:pax-logging-log4j2`	≥ 1.11.0&&< 1.11.11	1.11.11
☕Maven	`org.ops4j.pax.logging:pax-logging-log4j2`	≥ 2.0.0&&< 2.0.12	2.0.12

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.