# CVE-2021-45046: Apache Log4j2 Thread Context Message Pattern and Context Lookup Pattern vulnerable to a denial of service attack

> CVE-2021-45046: Apache Log4j2 Thread Context Message Pattern and Context Lookup Pattern vulnerable to a denial of service attack. CVSS 9.0 (CVSS 3.1), in CISA KEV.

Canonical: https://rewindex.com/cve/CVE-2021-45046
Last updated: 2025-10-21T23:25:22Z

- Published: 2021-12-14 16:55 UTC · Updated: 2025-10-21 23:25 UTC · Assigner: apache
- CVSS: 9.0 (CVSS 3.1) · Severity: Critical · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
- EPSS: 100.0%, 100th percentile (scored 2026-10-25)
- CISA KEV: yes, added 2023-05-01, federal due date 2023-05-22, ransomware use: Known
- CWE: CWE-917

## 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.

## CISA required action

Apply updates per vendor instructions.

## Affected vendors and products

- Apache Software Foundation: Apache Log4j

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2021-45046)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2021-45046)
- [https://cert-portal.siemens.com/productcert/pdf/ssa-397453.pdf](https://cert-portal.siemens.com/productcert/pdf/ssa-397453.pdf)
- [https://cert-portal.siemens.com/productcert/pdf/ssa-479842.pdf](https://cert-portal.siemens.com/productcert/pdf/ssa-479842.pdf)
- [https://cert-portal.siemens.com/productcert/pdf/ssa-661247.pdf](https://cert-portal.siemens.com/productcert/pdf/ssa-661247.pdf)
- [https://cert-portal.siemens.com/productcert/pdf/ssa-714170.pdf](https://cert-portal.siemens.com/productcert/pdf/ssa-714170.pdf)
- [https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EOKPQGV24RRBBI4TBZUDQMM4MEH7MXCY/](https://lists.fedoraproject.org/archives/list/package-announce%2540lists.fedoraproject.org/message/EOKPQGV24RRBBI4TBZUDQMM4MEH7MXCY/)
- [https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SIG7FZULMNK2XF6FZRU4VWYDQXNMUGAJ/](https://lists.fedoraproject.org/archives/list/package-announce%2540lists.fedoraproject.org/message/SIG7FZULMNK2XF6FZRU4VWYDQXNMUGAJ/)
- [https://logging.apache.org/log4j/2.x/security.html](https://logging.apache.org/log4j/2.x/security.html)
- [https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0032](https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0032)
- [https://security.gentoo.org/glsa/202310-16](https://security.gentoo.org/glsa/202310-16)
- [https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-log4j-qRuKNEbd](https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-log4j-qRuKNEbd)
- [https://www.cve.org/CVERecord?id=CVE-2021-44228](https://www.cve.org/CVERecord?id=CVE-2021-44228)
- [https://www.debian.org/security/2021/dsa-5022](https://www.debian.org/security/2021/dsa-5022)
- [https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00646.html](https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00646.html)
- [https://www.kb.cert.org/vuls/id/930724](https://www.kb.cert.org/vuls/id/930724)
- [https://www.oracle.com/security-alerts/alert-cve-2021-44228.html](https://www.oracle.com/security-alerts/alert-cve-2021-44228.html)
- [https://www.oracle.com/security-alerts/cpuapr2022.html](https://www.oracle.com/security-alerts/cpuapr2022.html)
- [https://www.oracle.com/security-alerts/cpujan2022.html](https://www.oracle.com/security-alerts/cpujan2022.html)
- [https://www.oracle.com/security-alerts/cpujul2022.html](https://www.oracle.com/security-alerts/cpujul2022.html)
- [http://www.openwall.com/lists/oss-security/2021/12/14/4](http://www.openwall.com/lists/oss-security/2021/12/14/4)
- [http://www.openwall.com/lists/oss-security/2021/12/15/3](http://www.openwall.com/lists/oss-security/2021/12/15/3)
- [http://www.openwall.com/lists/oss-security/2021/12/18/1](http://www.openwall.com/lists/oss-security/2021/12/18/1)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2021-45046 · Markdown: https://rewindex.com/cve/CVE-2021-45046.md · JSON: https://rewindex.com/api/v1/cves/CVE-2021-45046 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:15:53.319Z