Skip to content

Apache Tomcat has an Improper Encoding or Escaping of Output vulnerability in the JsonAccessLogValve

High severity GitHub Reviewed Published Apr 9, 2026 to the GitHub Advisory Database • Updated Apr 10, 2026

Package

maven org.apache.tomcat.embed:tomcat-embed-core (Maven)

Affected versions

>= 9.0.40, < 9.0.116
>= 10.1.0-M1, < 10.1.54
>= 11.0.0-M1, < 11.0.21

Patched versions

9.0.116
10.1.54
11.0.21
maven org.apache.tomcat:tomcat (Maven)
>= 9.0.40, < 9.0.116
>= 10.1.0-M1, < 10.1.54
>= 11.0.0-M1, < 11.0.21
9.0.116
10.1.54
11.0.21
maven org.apache.tomcat:tomcat-catalina (Maven)
>= 9.0.40, < 9.0.116
>= 10.1.0-M1, < 10.1.54
>= 11.0.0-M1, < 11.0.21
9.0.116
10.1.54
11.0.21

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.

References

Published by the National Vulnerability Database Apr 9, 2026
Published to the GitHub Advisory Database Apr 9, 2026
Reviewed Apr 10, 2026
Last updated Apr 10, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(38th percentile)

Weaknesses

Improper Encoding or Escaping of Output

The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved. Learn more on MITRE.

CVE ID

CVE-2026-34483

GHSA ID

GHSA-rv64-5gf8-9qq8

Source code

Loading Checking history
See something to contribute? Suggest improvements for this vulnerability.