ZDF
Sign inSign up

Vulnerabilities

Vulnerability · CVE-2026-34481

Apache Log4j's JsonTemplateLayout https://logging.apache.org/log4j/2.x/manual/json-template-layout.html , in versions up to and including 2.25.3, produces invalid JSON…

Published Apr 10, 2026 · catalog updated Jul 11, 2026 · Apache

Check if you run it

No confirmed exploitation is on record for CVE-2026-34481. EPSS is 0.85%. Act only if a listed version of Apache is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium6.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.85%
Remediation
Advisory link
Affected products
cpe apache/log4j

Apache Log4j's JsonTemplateLayout https://logging.apache.org/log4j/2.x/manual/json-template-layout.html , in versions up to and including 2.25.3, produces invalid JSON output when log events contain non-finite floating-point values (NaN, Infinity, or -Infinity), which are prohibited by RFC 8259. This may cause downstream log processing systems to reject or fail to index affected records. An attacker can exploit this issue only if both of the following conditions are met: * The application uses JsonTemplateLayout. * The application logs a MapMessage, or logs an object directly (e.g., via Logger.info(Object), which wraps it in an ObjectMessage), where the message contains an attacker-controlled floating-point value. Users are advised to upgrade to Apache Log4j JSON Template Layout 2.25.4, which corrects this issue. Note: The fix released in version 2.25.4 did not cover all affected code paths. CVE-2026-49844 was assigned to the remaining issue, which concerns the MapMessage.asJson() serialization in Apache Log4j API and is fixed in versions 2.25.5 and 2.26.1.

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/log4j3.0.0

How to fix CVE-2026-34481

What to do

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

Should you patch?

No confirmed exploitation is on record for CVE-2026-34481. EPSS is 0.85%. Act only if a listed version of Apache is installed.

Which versions are affected?

Compare what you have installed with 3.0.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-116. EPSS 0.85%. There is no CISA KEV listing. 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.

Timeline

Detection, updates, and resolution for this record.

  1. Jul 11, 2026 · NIST NVD

    Updated

    Apache Log4j's JsonTemplateLayout https://logging.apache.org/log4j/2.x/manual/json-template-layout.html , in versions up to and including 2.25.3, produces invalid JSON output when log events contain non-finite floating-point values (NaN, Infinity, or -Infinity), which are prohibited by RFC 8259. This may cause downstream log processing systems to reject or fail to index affected records. An attack

  2. Oct 15, 2026 · Apache Software Foundation

    Detected

    Named on the public Apache Software Foundation page.

Sources

  • Apache Software FoundationVendor advisoryCVE-2026-34481

    CVE-2026-34481 is named on the public Apache Software Foundation page.

    logging.apache.org
  • CVE.orgVulnerability recordCVE-2026-34481

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-34481

    30-day exploitation probability 0.9%

    first.org
  • NIST NVDVulnerability recordCVE-2026-34481

    Apache Log4j's JsonTemplateLayout https://logging.apache.org/log4j/2.x/manual/json-template-layout.html , in versions up to and including 2.25.3, produces invalid JSON output when log events contain non-finite floating-point values (NaN, Infinity, or -Infinity), which are prohib

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.