CVE-2026-59099

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 4.0

9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS 3.1

9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS

0.5% chance of exploitation in the next 30 days; higher than 45% of CVEs (scores of 2026-10-25)

CWE

CWE-323

Published

2026-07-02

Modified

2026-10-25

Record from

the NVD, synced 2026-10-25

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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