# CVE-2026-87022: Apache Tomcat WebSocket message smuggling in per-message-deflate

Source: https://junglewise.ai/threats/cve-2026-87022-improper-handling-of-length-parameter-inconsistency-vulnerability  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-23. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-87022 · Severity: high · CVSS 7.5 · Published 2026-09-23

Apache Tomcat is a web server widely used to host Java applications. When WebSocket compression (per-message-deflate) is enabled, a flaw in how Tomcat handles message length parameters allows an attacker to inject crafted messages that bypass validation, potentially leading to message smuggling attacks that can compromise application logic or enable session hijacking.

Technologies: [Apache Tomcat](https://junglewise.ai/threats/technologies/tomcat). Vendors: [Apache](https://junglewise.ai/threats/vendors/apache).

## Quick answers

**Is CVE-2026-87022 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-87022 being exploited in the wild.

**How severe is CVE-2026-87022?** High severity, with a CVSS score of 7.5, published 23 September 2026.

**Which products and versions are affected?** Apache Tomcat 11.0.0-M1 through 11.0.25, 10.1.0-M1 through 10.1.59, 9.0.0-M1 through 9.0.121, 8.5.0 through 8.5.100, 7.0.56 through 7.0.109.

**Is there a fix for CVE-2026-87022?** A patch was published on 2026-09-23: Fixes available in Tomcat 11.0.26, 10.1.60, 9.0.122 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-87022 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-87022?** Check whether you run Apache Tomcat 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.

## Technical details

The vulnerability exists in Tomcat's WebSocket implementation when per-message-deflate compression is active. Improper validation of length parameters during decompression allows an attacker to craft WebSocket frames that are processed inconsistently, enabling message smuggling. The flaw affects multiple major versions and requires an active WebSocket connection from a network-accessible attacker.

## Affected products

- Apache Tomcat 11.0.0-M1 through 11.0.25, 10.1.0-M1 through 10.1.59, 9.0.0-M1 through 9.0.121, 8.5.0 through 8.5.100, 7.0.56 through 7.0.109

## Timeline

- 2026-09-23: disclosed: CVE-2026-87022 publicly disclosed
- 2026-09-23: patched: Fixes available in Tomcat 11.0.26, 10.1.60, 9.0.122

## References

- [https://lists.apache.org/thread/ypvlkjqsq0480fnk9jm6h9qllddwlw4w](https://lists.apache.org/thread/ypvlkjqsq0480fnk9jm6h9qllddwlw4w)
- [http://www.openwall.com/lists/oss-security/2026/09/23/30](http://www.openwall.com/lists/oss-security/2026/09/23/30)

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