# CVE-2026-34483: Apache Tomcat improper output escaping in JsonAccessLogValve

Source: https://junglewise.ai/threats/cve-2026-34483-apache-tomcat-improper-output-escaping-in-jsonaccesslogvalve  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-09. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

CVE-2026-34483 · Severity: high · CVSS 7.5 · Published 2026-04-09

Apache Tomcat, a widely used web server and application container, contains a vulnerability in its JSON logging component. This flaw allows for improper data formatting in access logs, which could lead to the exposure of sensitive information or interfere with log monitoring systems. Organizations using affected versions should upgrade to ensure their application logs remain secure and accurate.

Technologies: [Apache Tomcat](https://junglewise.ai/threats/technologies/tomcat), [org.apache.tomcat:tomcat (Maven)](https://junglewise.ai/threats/technologies/org-apache-tomcat-tomcat), [org.apache.tomcat:tomcat-catalina (Maven)](https://junglewise.ai/threats/technologies/org-apache-tomcat-tomcat-catalina), [org.apache.tomcat.embed:tomcat-embed-core (Maven)](https://junglewise.ai/threats/technologies/org-apache-tomcat-embed-tomcat-embed-core). Vendors: [Apache](https://junglewise.ai/threats/vendors/apache), [Maven](https://junglewise.ai/threats/vendors/maven).

## Quick answers

**Is CVE-2026-34483 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-34483 being exploited in the wild.

**How severe is CVE-2026-34483?** High severity, with a CVSS score of 7.5, published 9 April 2026.

**Which products and versions are affected?** org.apache.tomcat:tomcat (Maven) ECOSYSTEM:introduced=9.0.40,fixed=9.0.116; org.apache.tomcat:tomcat-catalina (Maven) ECOSYSTEM:introduced=9.0.40,fixed=9.0.116; org.apache.tomcat.embed:tomcat-embed-core (Maven) ECOSYSTEM:introduced=9.0.40,fixed=9.0.116.

**Is there a fix for CVE-2026-34483?** Yes. org.apache.tomcat:tomcat (Maven): upgrade to 9.0.116 or later; org.apache.tomcat:tomcat-catalina (Maven): upgrade to 9.0.116 or later; org.apache.tomcat.embed:tomcat-embed-core (Maven): upgrade to 9.0.116 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-34483 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-34483?** Check whether you run Apache Tomcat, org.apache.tomcat:tomcat (Maven), org.apache.tomcat:tomcat-catalina (Maven) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- org.apache.tomcat:tomcat (Maven): upgrade to 9.0.116 or later

  ```sh
  # set org.apache.tomcat:tomcat to 9.0.116 in your pom.xml or build.gradle
  ```

- org.apache.tomcat:tomcat-catalina (Maven): upgrade to 9.0.116 or later

  ```sh
  # set org.apache.tomcat:tomcat-catalina to 9.0.116 in your pom.xml or build.gradle
  ```

- org.apache.tomcat.embed:tomcat-embed-core (Maven): upgrade to 9.0.116 or later

  ```sh
  # set org.apache.tomcat.embed:tomcat-embed-core to 9.0.116 in your pom.xml or build.gradle
  ```


## Technical details

An Improper Encoding or Escaping of Output vulnerability (CWE-116) exists in the JsonAccessLogValve component of Apache Tomcat. The vulnerability stems from incomplete escaping of data when generating JSON-formatted access logs. A remote, unauthenticated attacker can exploit this by sending specially crafted requests that, when logged, break the JSON structure or inject unexpected content. This can lead to the disclosure of sensitive information or the manipulation of log data consumed by downstream analysis tools. The issue is resolved in versions 11.0.21, 10.1.54, and 9.0.117.

## Affected products

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

## Identifiers

- CVE-2026-34483
- GHSA-rv64-5gf8-9qq8

## Timeline

- 2026-04-09: disclosed
- 2026-04-09: advisory
- 2026-04-09: patched

## References

- [https://lists.apache.org/thread/j1w7304yonlr8vo1tkb5nfs7od1y228b](https://lists.apache.org/thread/j1w7304yonlr8vo1tkb5nfs7od1y228b)
- [http://www.openwall.com/lists/oss-security/2026/04/09/26](http://www.openwall.com/lists/oss-security/2026/04/09/26)

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