CVE-2026-34483: Apache Tomcat: Incomplete escaping of JSON access logs

[Mark Thomas <markt () apache org>]

Severity: low

Affected versions:

- Apache Tomcat 11.0.0-M1 through 11.0.20
- Apache Tomcat 10.1.0-M1 through 10.1.53
- Apache Tomcat 9.0.40 through 9.0.116
- Apache Tomcat 8.5.84 through 8.5.100
- Apache Tomcat through 8.5.83 unaffected

Description:

Improper Encoding or Escaping of Output vulnerability in the 
JsonAccessLogValve component of Apache Tomcat.

This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.20, from 
10.1.0-M1 through 10.1.53, from 9.0.40 through 9.0.116.

Users are recommended to upgrade to version 11.0.21, 10.1.54 or 9.0.117 
, which fix the issue.

Credit:

Bartlomiej Dmitruk, striga.ai (finder)

References:

https://lists.apache.org/thread/j1w7304yonlr8vo1tkb5nfs7od1y228b
https://tomcat.apache.org/
https://www.cve.org/CVERecord?id=CVE-2026-34483