CVE-2026-76183: Authentication Bypass by Alternate Name vulnerability in Apache Tomcat allowed the security constraints for an

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CRITICAL 9.8REMOTEWATCHLIST

CVE-2026-76183 is a critical-severity flaw (CVSS 9.8) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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. The following versions were EOS at the time the CVE was created but are known to be affected: from 8.5.0 through 8.5.100, from 7.0.43 through 7.0.109. Other unsupporte

Why this priority

Critical severity
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 53%)
CISA exploited list	No
Weakness	CWE-289
Published	2026-09-23
Last modified	2026-09-30

Publisher (CNA): Apache Software Foundation

Last updated 2026-09-30 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Timeline

2026-09-23 12:17 UTCPublished CVE record published
2026-09-30 15:22 UTCUpdated Record last modified

Exact fixes by distribution

Fedora 46 · fio · FIXED · 3.43-2.fc46 · FEDORA-2026-b36219886b · source

sudo dnf upgrade --advisory=FEDORA-2026-b36219886b

Fedora ELN · weston · FIXED · 16.0.2-1.eln159 · FEDORA-2026-b98ccaa6a0 · source

sudo dnf upgrade --advisory=FEDORA-2026-b98ccaa6a0

Debian 12 · tomcat10 · NO FIX YET

Debian 13 · tomcat10 · NO FIX YET

Debian 13 · tomcat11 · NO FIX YET

Debian 12 · tomcat9 · FIXED · 9.0.70-2

sudo apt update && sudo apt install --only-upgrade tomcat9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' tomcat9)" ge "9.0.70-2" && echo PATCHED || echo STILL-VULNERABLE

RHEL 10 · tomcat · NO FIX YET

RHEL 10 · tomcat9 · NO FIX YET

RHEL 6 · tomcat6 · NOT AFFECTED

RHEL 7 · tomcat · DEFERRED

RHEL 8 · pki-deps:10.6/pki-servlet-engine · DEFERRED

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2026-3166 · source

sudo dnf update --advisory=ALAS2023-2026-3166

Amazon Linux 2 · see advisory · FIXED · ALAS2-2026-4019 · source

sudo yum update --advisory=ALAS2-2026-4019

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: Ethen1212/tomcat-CVE-2026-76183 (1 stars)

Advisories and coverage

Official advisories

Amazon Linux 2 ALAS: ALAS2-2026-4019 (important): tomcat 2026-10-24
Amazon Linux 2023 ALAS: ALAS2023-2026-3165 (important): tomcat10 2026-10-12
Amazon Linux 2023 ALAS: ALAS2023-2026-3166 (important): tomcat9 2026-10-12
Amazon Linux 2 ALAS: ALAS2TOMCAT9-2026-029 (important): tomcat 2026-10-12

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-76183?

No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.

Is CVE-2026-76183 being exploited?

CVE-2026-76183 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-76183 affect?

CVE-2026-76183 affects affected software. Severity is critical (CVSS 9.8). 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 1

How urgent is CVE-2026-76183?

Priority 59/100. Critical severity; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Apache Tomcat vulnerabilities

References

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