9.3

CVE-2026-59099: apereo cas Reusing a Nonce, Key Pair in Encryption

CVSS: 9.3v4.0CriticalAwaiting analysis
Published 02-07-2026Last modified 14-07-2026
Open JSON

Vulnerability summary

CVE-2026-59099 is a critical (CVSS 9.3) Reusing a Nonce, Key Pair in Encryption vulnerability in apereo cas. EPSS estimates a 0.55% chance of exploitation in the next 30 days, higher than 44.8% of scored vulnerabilities. 1 public exploit is recorded.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.3/10
010
Critical · v4.0 (CVE.org)
EPSS score
0.55%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits1github

Timeline

  1. 02-07-2026
    PublishedVulnerability first disclosed.
  2. 14-07-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

4 scores · 2 sources · 2 versions

EPSS trend

Probability

0.55%

Chance of exploitation in the next 30 days

Percentile

45%

Versus all other CVEs

30-day change

0.00 pp

From 0.55% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.55%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

1 found
  • githubUnverified

    Oss

    Maturity: poc

Weaknesses

CWE · root cause

Affected systems

Apereo1 product
  • cas≥ 7.3.0, < 8.0.0-RC6

1 vendor · 1 product

References

5 links