CVE-2026-59099
CRITICALDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 28% of all known CVEs.
References
Related Vulnerabilities
Other CWE-323 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2017-13082 | High | 8.1 | 4.6% | - | Fix |
| CVE-2026-49952 | Critical | 9.1 | 4.2% | - | - |
| CVE-2017-7902 | Critical | 9.8 | 2.6% | - | - |
| CVE-2017-13080 | Medium | 5.3 | 2.3% | - | Fix |
| CVE-2017-13084 | Medium | 6.8 | 2.2% | - | - |
| CVE-2017-13079 | Medium | 5.3 | 2.1% | - | Fix |
Common questions
How do I fix CVE-2026-59099?
No published fix for CVE-2026-59099 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-59099 being actively exploited?
Not that we know of. CVE-2026-59099 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.36% is the estimated probability that it will be exploited in the next 30 days. That is higher than 28% of all scored CVEs.
How severe is CVE-2026-59099?
CVE-2026-59099 has a CVSS v3 base score of 9.1, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-14.