ZeroDay Findings
Sign inSign up

Findings

CVE-2021-45046

Apache Log4j2 Deserialization of Untrusted Data Vulnerability

Published Dec 14, 2021 · updated Jun 16, 2026 · apache log4j

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.

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

Required action

Apply updates per vendor instructions.

CISA due date May 22, 2023

Affected

  • cpe apache/log4jversion unspecified
  • 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

Sources

  • CISA KEVCVE-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.orgCVE-2021-45046

    Official CVE identifier

    cve.org
  • FIRST EPSSCVE-2021-45046

    30-day exploitation probability 100.0%

    first.org
  • Metasploit Modulesauxiliary_scanner/http/log4shell_scanner

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

    rapid7.com
  • NIST NVDCVE-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

References