Vulnerability · Published Jul 24, 2026 · Assigned by CERT-PL
CVE-2026-15243Improper Validation of Certificate in CAS Client
High 7.4
In plain English
A high-severity security flaw in Jasig CAS Client from Apereo. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 18% of all known vulnerabilities).
Official description
Apereo CAS Client accepts any CA-trusted certificate for any hostname, provided the URL the client is calling matches the configured allowlist or regex. An attacker with a MITM position (DNS poisoning, rogue Wi-Fi, malicious proxy, etc.) can provide any CA-signed certificate for a hostname that matches the configured allowlist or regex. This can lead to intercepting the CAS exchange, capturing the Ticket-Granting Ticket (TGT), and subsequently obtaining Service Tickets on behalf of the victim. Because maintainers contact attempts were unsuccessful, vulnerabilities have only been confirmed in version 4.1.0 (Java Apereo CAS Client) and 3.6.4 (Jasig CAS Client) but may also affect other versions.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Apereo | Java Apereo CAS Client | 4.1.0 |
| Apereo | Jasig CAS Client | 3.6.4 |
Weakness: CWE-297 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
References
- https://cert.pl/en/posts/2026/07/CVE-2026-15243 third-party-advisory
- https://www.apereo.org/programs/software/cas product