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CVE-2026-15243 is an improper certificate validation flaw in Apereo CAS Client and Jasig CAS Client. The client accepts any certificate signed by a trusted certificate authority for any hostname, as long as the URL being accessed matches a configured allowlist or regular expression. This results in hostname validation not being correctly enforced during TLS certificate verification. The issue has been confirmed in Java Apereo CAS Client 4.1.0 and Jasig CAS Client 3.6.4, and other versions may also be affected. In a man-in-the-middle scenario, an attacker can present a CA-signed certificate for a matching hostname, intercept the CAS authentication exchange, and compromise the integrity and confidentiality of the authentication flow.
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2 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An improper certificate validation vulnerability affecting Apereo CAS Client software.
An improper certificate hostname validation flaw in Apereo CAS Client / Jasig CAS Client that allows acceptance of any CA-trusted certificate for a hostname matching the configured allowlist or regex, enabling man-in-the-middle interception of CAS authentication exchanges and theft of TGTs and service tickets.
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.