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Vulnerabilities

Vulnerability · CVE-2021-4104

Apache log4j Deserialization of Untrusted Data

Published Apr 26, 2022 · catalog updated Apr 26, 2022 · Apache

Patch now

CVE-2021-4104 is in the CISA known-exploited catalog. Confirm Apache against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
Severity
Unknown—
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
80.60%
Remediation
Remediation guidance
Affected products
vendor Apache log4j

JMSAppender in Log4j 1.2 is vulnerable to deserialization of untrusted data when the attacker has write access to the Log4j configuration. The attacker can provide TopicBindingName and TopicConnectionFactoryBindingName configurations causing JMSAppender to perform JNDI requests that result in remote code execution in a similar fashion to CVE-2021-44228. Note this issue only affects Log4j 1.2 when specifically configured to use JMSAppender, which is not the default. Apache Log4j 1.2 reached end of life in August 2015. Users should upgrade to Log4j 2 as it addresses numerous other issues from th

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.

  • vendor Apache log4jversion unspecified

How to fix CVE-2021-4104

What to do

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

Should you patch?

CVE-2021-4104 is in the CISA known-exploited catalog. Confirm Apache against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Affected version ranges are not on this record. Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.

What should an analyst verify?

No weakness class is stored. EPSS 80.60%. The CISA KEV listing is the exploitation evidence. No Exploit-DB or Metasploit reference is linked. 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. Apr 26, 2022 · CISA KEV

    Known exploited

    Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.

  2. Oct 15, 2026 · Apache Software Foundation

    Detected

    Named on the public Apache Software Foundation page.

Sources

  • Apache Software FoundationVendor advisoryCVE-2021-4104

    CVE-2021-4104 is named on the public Apache Software Foundation page.

    logging.apache.org
  • CVE.orgVulnerability recordCVE-2021-4104

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-4104

    30-day exploitation probability 80.6%

    first.org
  • VulnCheck KEVConfirmed exploitationCVE-2021-4104

    JMSAppender in Log4j 1.2 is vulnerable to deserialization of untrusted data when the attacker has write access to the Log4j configuration. The attacker can provide TopicBindingName and TopicConnectionFactoryBindingName configurations causing JMSAppender to perform JNDI requests t

    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.