Apache Tomcat: authentication bypass

Apache Tomcat

Authentication Bypass by Alternate Name vulnerability in Apache Tomcat allowed the security constraints for any WebSocket endpoint to be bypassed. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.59, from 9.0.0.M1 through 9.0.121.

Do this now

Review WebSocket endpoint security constraints in Apache Tomcat and apply the fixed release when available.

First seen: 23 Oct 2026
Last update: 23 Oct 2026, 19:39 UTC
Identifiers: CVE-2026-76183
CVSS: 9.8
Source: news
On the menu as: Java

Check this repository for exposure to one security incident from pwned.coffee. Report first, change nothing until I say so.

## Apache Tomcat: authentication bypass
Severity: critical. Patch status: fix status unknown.
Affected: Apache Tomcat
Ids: CVE-2026-76183

Authentication Bypass by Alternate Name vulnerability in Apache Tomcat allowed the security constraints for any WebSocket endpoint to be bypassed. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.59, from 9.0.0.M1 through 9.0.121.

## Steps
1. Search the repo, its CI and infra config for Apache Tomcat. If present, report the version in use and whether it's affected.
2. There is no fix yet. Until one ships: Authentication Bypass by Alternate Name vulnerability in Apache Tomcat allowed the security constraints for any WebSocket endpoint to be bypassed. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.59, from 9.0.0.M1 through 9.0.121.

## Report
A table: file, product or package, version in use, affected yes/no, exact fix. Then anything a human has to check outside the repo.

If you have the pwned.coffee MCP server (https://pwned.coffee/mcp), call lookup_cve("CVE-2026-76183") for the latest, and check_repo with this repo's lockfiles, Dockerfiles and workflows for a full receipt.
Sources: https://lists.apache.org/thread/45mxk8nj2q8pkhct6lfxkvtm2jpywrsp https://nvd.nist.gov/vuln/detail/CVE-2026-76183
https://pwned.coffee/i/authentication-bypass-by-alternate-name-vulnerability-in-cve-2026-76183

Timeline

23 Oct 2026, 19:40 UTC
Proof-of-concept code for CVE-2026-76183 is public on GitHub. Unverified, but expect scanning to follow.
23 Oct 2026
First reported.

Sources

Totalone very hot coffee