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Vulnerabilities

Vulnerability · CVE-2021-45046

Apache Log4j2 Deserialization of Untrusted Data Vulnerability

Published Dec 6, 2021 · catalog updated Jun 16, 2026 · Apache Log4j2

Patch now

CVE-2021-45046 is in the CISA known-exploited catalog, due May 22, 2023. Confirm Apache Log4j2 against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Severity
Critical9.0
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
99.98%
Remediation
Remediation guidance
Affected products
cpe apache/log4j · cpe cvat/computer vision annotation tool · cpe debian/debian linux · cpe intel/audio development kit · cpe siemens/captial · cpe siemens/sppa-t3000 ses3000 firmware

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe apache/log4j2.0
  • cpe cvat/computer vision annotation toolversion unspecified
  • cpe debian/debian linux10.0
  • cpe intel/audio development kitversion unspecified
  • cpe siemens/captialversion unspecified
  • cpe siemens/sppa-t3000 ses3000 firmwareversion unspecified
  • cpe sonicwall/email securityversion unspecified
  • vendor Apache Log4j2version unspecified

How to fix CVE-2021-45046

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2021-45046 is in the CISA known-exploited catalog, due May 22, 2023. Confirm Apache Log4j2 against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Compare what you have installed with debian/debian linux 10.0. Apply updates per vendor instructions.

What should an analyst verify?

CWE-917: Expression Language Injection. EPSS 99.98%. The CISA KEV listing is the exploitation evidence. A public exploit reference is linked in Sources. That is not the same as confirmed exploitation. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Dec 14, 2021 · Catalog

    Detected

    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 mal

  2. May 1, 2023 · CISA KEV

    Known exploited

    Apply updates per vendor instructions.

  3. May 22, 2023 · CISA KEV

    Remediation due

    Apply updates per vendor instructions.

  4. Jun 16, 2026 · Catalog

    Updated

    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 mal

Sources

  • Apache Software FoundationVendor advisoryCVE-2021-45046

    CVE-2021-45046 is named on the public Apache Software Foundation page.

    logging.apache.org
  • CISA KEVConfirmed exploitationCVE-2021-45046

    Apache Log4j2 contains a deserialization of untrusted data vulnerability due to the incomplete fix of CVE-2021-44228, where the Thread Context Lookup Pattern is vulnerable to remote code execution in certain non-default configurations.

    cisa.gov
  • CVE.orgVulnerability recordCVE-2021-45046

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-45046

    30-day exploitation probability 100.0%

    first.org
  • Metasploit ModulesPublic exploit moduleauxiliary_scanner/http/log4shell_scanner

    Public module reference (normal). Module source is not copied into this catalog.

    rapid7.com
  • NIST NVDVulnerability recordCVE-2021-45046

    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

    nvd.nist.gov
  • VulnCheck KEVConfirmed exploitationCVE-2021-45046

    Apache Log4j2 contains a deserialization of untrusted data vulnerability due to the incomplete fix of CVE-2021-44228, where the Thread Context Lookup Pattern is vulnerable to remote code execution in certain non-default configurations.

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.