PT-2026-55299 · Apereo · Apereo Cas

George Chen · Published 2026-07-02 · Updated 2026-07-03 · CVE-2026-59099

Positive Technologies (AI Summary)

CVSS v3.1

9.1

Critical

Base vector

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

Name of the Vulnerable Software and Affected Versions Apereo CAS versions 7.3.0 through 8.0.0-RC5

Description A cryptographic issue allows remote unauthenticated attackers to recover plaintext conversation state. This occurs because the system reuses the AES-GCM initialization vector (IV) across the server lifetime. By collecting multiple client-side webflow execution tokens from the unauthenticated login page, an attacker can perform known-plaintext analysis to decrypt the webflow conversation state. This is possible due to keystream reuse resulting from a fixed all-zero IV paired with the same encryption key.

Recommendations Update to version 8.0.0-RC6 or later.

Exploit

Fix

Weakness Enumeration

CWE-323

Related Identifiers

CVE-2026-59099

Affected Products

Apereo Cas

References · 11

• 🔥 https://github.com/geo-chen/oss/blob/main/cas.md · Exploit
• https://github.com/apereo/cas/commit/22c6f4adf738852782309b523b4e80371057f2d0 · Patch
• https://apereo.github.io/2026/06/18/vuln · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-59099 · Security Note
• https://github.com/apereo/cas/releases/tag/v8.0.0-RC6 · Note
• https://twitter.com/CVEnew/status/2072814585372172582 · Twitter Post
• https://vulncheck.com/advisories/apereo-cas-rc6-aes-gcm-nonce-reuse-information-disclosure · Note
• https://reddit.com/r/pwnhub/comments/1um44r3/apereo_cas_730_before_800rc6_contains_a · Reddit Post
• https://twitter.com/OrizonCyber/status/2072817632470823300 · Twitter Post
• https://twitter.com/infoflowcloud/status/2072815528263983446 · Twitter Post
• https://twitter.com/ThreatAft/status/2072888894685843890 · Twitter Post