Jenkins SAML Plugin CVE-2025-64131

Exploitation requires the Jenkins SAML Plugin (version 4.583.vc68232f7018a_ or earlier) to be installed and configured as the security realm. The attacker must be able to obtain the SAML authentication flow (the request/response/assertion) exchanged between a legitimate user's browser and Jenkins - e.g., through network interception, a man-in-the-middle position, or access to captured SAML messages - and a real user must perform that authentication (UI:R). The limiting factors are significant: the attacker cannot forge authentication out of nothing but must capture a genuine flow (reflected in AC:H), and success depends on a victim actually authenticating; instances not using the SAML plugin are unaffected.

Signals are moderate and internally consistent, pointing to a real-but-conditional risk rather than a drop-everything emergency. The CVSS 3.1 vector (AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H, 7.5 HIGH) describes unauthenticated network exploitation leading to full session/account takeover, but two metrics meaningfully constrain it: AC:H means the attacker must first obtain information about the SAML authentication flow between the victim's browser and Jenkins, and UI:R means a legitimate user must actually perform an authentication the attacker can capture and replay. EPSS is low at 0.47% (39th percentile), which aligns with the high attack complexity and the lack of a public exploit - this is not a signal of imminent mass exploitation. There is no CISA KEV listing and no POC referenced in the provided data, so exploitation is theoretical at time of analysis. The CWE-294 (Authentication Bypass by Capture-Replay) classification matches the description precisely. Net: a genuine authentication-bypass weakness worth patching on a normal priority cycle for Jenkins instances using the SAML plugin, but the capture-and-replay prerequisite and required user interaction make widespread opportunistic exploitation unlikely. One data note: the 'Information Disclosure' tag understates the issue - the root impact is authentication bypass/account takeover, not mere disclosure.

An attacker positioned to observe the SAML authentication exchange between a victim's browser and Jenkins (for example via a malicious proxy, network interception, or captured/logged SAML response) saves the authentication request/response. Because the plugin maintains no replay cache, the attacker resubmits the captured SAML assertion and is authenticated to Jenkins as that user. No public exploit code is identified at time of analysis, and the high attack complexity requires the attacker to first obtain the live authentication flow.