GPUStack: SAML callback authentication bypass (CVE-2026-102894)

GPUStack versions 0.7.1 through 2.2.1 contain a critical authentication bypass vulnerability due to improper handling of SAML assertions. The application fails to verify the SAML response signature, issuer, audience, destination, or time conditions using the expected OneLogin_Saml2_Auth.process_response() function. This vulnerability is active regardless of whether SAML SSO is configured, allowing an attacker to reach the /auth/saml/callback endpoint and authenticate as any user by posting a forged XML payload. Successful exploitation results in account takeover, including administrative access, and allows for infinite replay of captured assertions.

Impact

Successful exploitation grants an attacker full access to the target GPUStack deployment and any managed infrastructure. The vulnerability allows for identity spoofing of existing administrative users. Because the affected endpoint is enabled by default, all installations prior to 2.2.2 are at risk.

Recommendation

• Upgrade GPUStack to version 2.2.2 or later immediately to patch CVE-2026-102894.
• Until patching, block network access to the /auth/saml/callback URI at the reverse proxy or ingress level.
• Audit existing user sessions and logs for anomalous successful authentication events originating from unexpected or untrusted network sources.