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CISA KEV · Known exploitedCritical

CVE-2021-45046

Apache Log4j2

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...

CVSS
9
EPSS
100.0%
100.0% percentile
CISA KEV
Listed
Published
2021.12.15
PRIORITY ASSESSMENT

Immediate review

CISA has listed this vulnerability in the Known Exploited Vulnerabilities catalog.

Known exploitationConfirmed by CISA KEV
Exploit probability100.0%
Technical severityCVSS 9

Vulnerability overview

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...

Affected product and versions

Product
Apache Log4j2
Affected versions
Apache Log4j2, >= 2.0.1 < 2.12.2, >= 2.13.0 < 2.16.0, 2.0, < 2019.1, 2019.1, 4.0, 4.1, 4.2, 5.0, 5.1, < 2021-12-13, 3.1, 8.5, 8.6, 8.7, 9.0, 3.7, 3.8, < 8.6.2j-398
Fixed versions
2.12.2, 2.16.0, 2019.1, 2021-12-13, 8.6.2j-398, 2021-12-11, 2020, 4.70, 2.30, 10.0.12, 2.7.0

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
CISA required action

Apply updates per vendor instructions.

Due date: 2023.05.22
  1. 1
    Identify

    Confirm that Apache Log4j2 and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
CWE
CWE-917
KEV added
2023.05.01
Ransomware use
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