GPUStack: SAML callback trusts an unverified SAMLResponse, allowing authentication bypass and account takeover

Summary

GPUStack is an open-source GPU cluster manager for AI model serving and GPU instance provisioning. From 0.7.1 until 2.2.2, the /auth/saml/callback endpoint decoded SAML XML, used its NameID and attributes to resolve or provision a user, and minted a gpustack_session JWT without calling OneLogin_Saml2_Auth.process_response to verify the signature, issuer, audience, destination, or time conditions. Any network client could submit an identity for an existing user, including an administrator, or provision a new non-administrator account, even when SAML was not configured. Response and Assertion identifiers were not consumed, so captured signed responses could also be replayed. This issue is fixed in version 2.2.2.

Remediation

1. Inventory every gpustack gpustack deployment, including staging.
2. No fixed version appears in the public sources yet. Check the references below and the vendor directly.

References

• Referencehttps://github.com/gpustack/gpustack/commit/705edbe1b5feec63959306daecd640e1c70eced2
• Referencehttps://github.com/gpustack/gpustack/commit/adc6d82be34e48390720a1361df616e2ea9d6d45
• Referencehttps://github.com/gpustack/gpustack/pull/5753
• Referencehttps://github.com/gpustack/gpustack/pull/5923
• Referencehttps://github.com/gpustack/gpustack/releases/tag/v2.2.2
• Referencehttps://github.com/gpustack/gpustack/security/advisories/GHSA-62m9-f875-rqw6