Vulnerability Description
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 containing an attacker-controlled floating-point value. Users are advised to upgrade to Apache Log4j JSON Template Layout 2.25.4, which corrects this issue.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Apache | Log4J | >= 2.14.0, < 2.25.4 |
Related Weaknesses (CWE)
References
- https://github.com/apache/logging-log4j2/pull/4080Issue Tracking
- https://lists.apache.org/thread/n34zdv00gbkdbzt2rx9rf5mqz6lhopcvMailing ListVendor Advisory
- https://logging.apache.org/cyclonedx/vdr.xmlProduct
- https://logging.apache.org/log4j/2.x/manual/json-template-layout.htmlTechnical Description
- https://logging.apache.org/security.html#CVE-2026-34481Vendor Advisory
- http://www.openwall.com/lists/oss-security/2026/04/10/10Mailing ListThird Party Advisory
FAQ
What is CVE-2026-34481?
CVE-2026-34481 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 ...
How severe is CVE-2026-34481?
CVE-2026-34481 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-34481?
Check the references section above for vendor advisories and patch information. Affected products include: Apache Log4J.