CVE-2026-59099

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 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 v3.1 Score

9.1
CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
NONE
Published: 7/2/2026Modified: 7/2/2026

Related Intelligence (1)

CRITICALVulnerability

NVD CRITICAL: CVE-2026-59099 — Apereo CAS 7.3.0 before 8.0.0-RC6 contains a cryptographic vulnerability that al...

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

CVE-2026-59099
NIST NVD

References (5)

https://apereo.github.io/2026/06/18/vuln/https://github.com/apereo/cas/commit/22c6f4adf738852782309b523b4e80371057f2d0https://github.com/apereo/cas/releases/tag/v8.0.0-RC6https://github.com/geo-chen/oss/blob/main/cas.mdhttps://www.vulncheck.com/advisories/apereo-cas-rc6-aes-gcm-nonce-reuse-information-disclosure