CVE-2026-15243 Improper Validation of Certificate in CAS Client
Attackers can bypass certificate validation in Apereo CAS Client to intercept authentication tickets via Man-in-the-Middle attacks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-15243?
CVE-2026-15243 is a high-severity vulnerability in Apereo Jasig CAS Client, published on 24 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
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.
Weakness: CWE-297
Which versions are affected by CVE-2026-15243?
How do I fix CVE-2026-15243?
No fix has been published for CVE-2026-15243 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-15243 being exploited?
There is no known exploitation of CVE-2026-15243 in the wild and no public exploit code.
Sources
Also known as GHSA-52jg-6vw4-42p8.