Vulnerability Description
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.
CVSS Score
CRITICAL
Related Weaknesses (CWE)
References
- https://apereo.github.io/2026/06/18/vuln/
- https://github.com/apereo/cas/commit/22c6f4adf738852782309b523b4e80371057f2d0
- https://github.com/apereo/cas/releases/tag/v8.0.0-RC6
- https://github.com/geo-chen/oss/blob/main/cas.md
- https://www.vulncheck.com/advisories/apereo-cas-rc6-aes-gcm-nonce-reuse-informat
FAQ
What is CVE-2026-59099?
CVE-2026-59099 is a vulnerability with a CVSS score of 9.1 (CRITICAL). 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 vecto...
How severe is CVE-2026-59099?
CVE-2026-59099 has been rated CRITICAL with a CVSS base score of 9.1/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-59099?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.