CVE-2021-45046
Apache Log4j2 Thread Context Message Pattern and Context Lookup Pattern vulnerable to a denial of service attack
Apache Log4j2 Deserialization of Untrusted Data Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.
Required action
Apply updates per vendor instructions.
CISA notes
https://logging.apache.org/log4j/2.x/security.html; https://nvd.nist.gov/vuln/detail/CVE-2021-45046
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.
Severity
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:HExploitation Context
as of October 14, 2026- CISA added CVE-2021-45046 to the KEV catalog 503 days after its CVE record was published. The median for entries added in 2023 is 12 days.
- It is one of 41 Apache entries in the CISA KEV catalog, and one of 5 added in 2023.
- Its current EPSS score (100.0%) is higher than that of 95% of CISA KEV entries.
Affected Products
| Vendor | Product | Affected versions |
|---|---|---|
| Apache Software Foundation | Apache Software Foundation Apache Log4j | Apache Log4j2 to <2.16.0 |
References
21 Links- [oss-security] 20211214 CVE-2021-45046: Apache Log4j2 Thread Context Message Pattern and Context Lookup Pattern vulnerable to a denial of service attack
- [oss-security] 20211215 Re: CVE-2021-45046: Apache Log4j2 Thread Context Message Pattern and Context Lookup Pattern vulnerable to a denial of service attack
- [oss-security] 20211218 Re: CVE-2021-45046: Apache Log4j2 Thread Context Message Pattern and Context Lookup Pattern vulnerable to a denial of service attack
- https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0032
- https://www.oracle.com/security-alerts/alert-cve-2021-44228.html
- https://www.cve.org/CVERecord?id=CVE-2021-44228
- https://logging.apache.org/log4j/2.x/security.html
- https://cert-portal.siemens.com/productcert/pdf/ssa-661247.pdf
- https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00646.html
- https://cert-portal.siemens.com/productcert/pdf/ssa-714170.pdf
- https://cert-portal.siemens.com/productcert/pdf/ssa-397453.pdf
- https://cert-portal.siemens.com/productcert/pdf/ssa-479842.pdf
- https://www.oracle.com/security-alerts/cpujan2022.html
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://www.oracle.com/security-alerts/cpujul2022.html
- https://security.gentoo.org/glsa/202310-16
Record Details
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Related
Tool categories
CVE record data © The MITRE Corporation, used under the CVE Terms of Use. Exploited-in-the-wild data from the CISA Known Exploited Vulnerabilities catalog (CC0). Exploit prediction scores by FIRST EPSS (first.org/epss). This site is not endorsed or certified by MITRE, NVD, CISA, or FIRST.