by Kastro
Paper/Archive/CVE-2026-59099

CVE-2026-59099

apereo cas — Apereo CAS 7.3.0 < 8.0.0-RC6 - AES-GCM Nonce Reuse Information Disclosure

EPSS 0.5%public exploitCVSS 9.3
critical.is priorityof 100
47
CVSS 9.3 (CNA)9.3 / 10 × 3027.9Not in CISA KEV+300.0EPSS percentile 45.9.459 × 209.2Exploit: SSVC poc+1010.0SSVC exploitation: poc+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
cas7.3.0 – < 8.0.0-RC68.0.0-RC6CNA

Scores by source

VulnCheck (CNA)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
VulnCheck (CNA)9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CISA ADPSSVCExploitation: poc · Automatable: yes · Technical impact: total

References

advisoryapereo.github.io/2026/06/18/vulnrefgithub.com/apereo/cas/releases/tag/v8.0.0-RC6exploitgithub.com/geo-chen/oss/blob/main/cas.mdpatchgithub.com/apereo/cas/commit/22c6f4adf738852782309b523b4e80371057f2d0writeupvulncheck.com/advisories/apereo-cas-rc6-aes-gcm-nonce-reuse-information-disclosure