CVE-2026-97791 Apache CXF: STSTokenValidator can accept untrusted SAML assertions because it shares validation state between requests

High 7.5 Published 9 Oct 2026 Updated 15 Oct 2026

Remote attackers can bypass SAML token validation in Apache CXF by exploiting a race condition in shared state, accepting forged assertions as trusted.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-97791?

CVE-2026-97791 is a high-severity vulnerability in Apache Cxf, published on 9 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

In Apache CXF, STSTokenValidator checks whether a SAML assertion is signed by a trusted certificate before deciding to send it to the STS. That result was stored in one object shared by all requests, so one request could read another's result. A remote, unauthenticated attacker could send a forged assertion signed with an untrusted certificate while legitimate requests were being processed, and it could be accepted as trusted without ever reaching the STS. Only services that use STSTokenValidator to validate SAML tokens without alwaysValidateToSts set are affected. Users are recommended to upgrade to versions 4.2.4 or 4.1.9 or 3.6.13, which fix this issue.

Weakness: CWE-362

Which versions are affected by CVE-2026-97791?

It affects 1 product.

Products include Apache Cxf.

How do I fix CVE-2026-97791?

Upgrade to a fixed version.

Is CVE-2026-97791 being exploited?

There is no known exploitation of CVE-2026-97791 in the wild and no public exploit code.

All Apache Cxf vulnerabilities

Sources

Also known as CLEANSTART-2026-YS58315, GHSA-2rg8-47cf-hp2j.