CVE-2026-59099: Apereo Cas

Critical severity, CVSS 9.1. EPSS: 0.5% chance of exploitation in the next 30 days.

Apereo CAS 7.3.0 before 8.0.0-RC6 contains a cryptographic vulnerability that allows remote unauthenticated attackers to recover plaintext conversation state by exploiting AES-GCM initialization vector reuse across the server lifetime. Attackers can collect multiple client-side webflow execution tokens from the unauthenticated login page and perform known-plaintext analysis to decrypt the webflow conversation state due to keystream reuse caused by a fixed all-zero IV paired with the same encryption key.

Affected products

• Apereo Cas: from 7.3.0, before 8.0.0-RC6 (fixed in 8.0.0-RC6)

Published 2026-07-02. Last modified 2026-07-14.