GHSA-5x9f-6vg5-qg4m: Omni has a TOCTOU race condition that allows multiple concurrent uses of a single-use SAML session token

Omni has a TOCTOU race condition (a timing bug where two operations that should be atomic happen separately, allowing a race between them) in its SAML authentication system. An attacker who intercepts a single-use SAML session token can send multiple concurrent requests with that token, and because the system checks if the token is used and then marks it used in two separate steps rather than one atomic operation, both requests can pass validation, allowing the attacker to authenticate as the victim multiple times.