What’s Vulnerable › Vulnerabilities

CVE-2026-59099: Apereo CAS 7.3.0 < 8.0.0-RC6 - AES-GCM Nonce Reuse Information Disclosure

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-02 · updated 2026-10-25
• Weakness: CWE-323

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.

Affected products

• Apereo CAS: from 7.3.0 before 8.0.0-RC6 — fixed in 8.0.0-RC6

How to fix

Upgrade to a fixed version: Apereo CAS 8.0.0-RC6. Check the vendor advisory for mitigations.

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-information-disclosure

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