Description

Jenkins SAML Plugin 4.618.v441a_27fa_46d2 and earlier allows overwriting the SAML identity provider metadata file through Stapler data binding, allowing attackers to replace it with attacker-controlled content and authenticate as any user.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-09-02T16:17:31.440Z",
  "pubdate": "2026-09-02T16:17:31.440Z",
  "executiveSummary": "The Jenkins SAML Plugin, specifically versions 4.618.v441a_27fa_46d2 and earlier, contains a critical vulnerability related to improper input validation within its Stapler data binding mechanism.\nThis vulnerability allows an attacker to manipulate the SAML identity provider (IdP) metadata file by overwriting it with arbitrary, attacker-controlled content.\nBy successfully replacing the legitimate IdP metadata, an attacker can bypass standard authentication controls, effectively enabling them to impersonate any user, including administrative accounts, within the Jenkins environment.\nThe vulnerability represents a severe risk to the integrity and confidentiality of the Jenkins instance, as it facilitates full account takeover without requiring knowledge of existing credentials.\nExploitation involves leveraging the Stapler data binding feature to inject malicious configuration data into the plugin's file storage, requiring no prior authentication to the vulnerable endpoint.",
  "technicalDetails": "The root cause of this vulnerability lies in the unsafe implementation of Stapler data binding within the Jenkins SAML Plugin. Stapler is the core web framework used by Jenkins, responsible for mapping HTTP requests to Java object properties.\nThe plugin improperly exposes the internal configuration management functionality, specifically the SAML IdP metadata file path, to user-controllable input via public setters or object constructors that Stapler automatically populates during request processing.\nAn attacker can craft a malicious HTTP request that exploits the Stapler binding mechanism to overwrite the locally stored SAML IdP metadata XML file. Because the application logic fails to perform adequate validation or sanitization on the source of the metadata, it blindly accepts the attacker-provided content.\nThe attack flow proceeds as follows: First, the attacker identifies the specific Stapler-bound endpoint associated with the SAML plugin configuration. Second, the attacker sends a specially crafted POST request containing the new metadata payload. Third, the plugin processes the request and persists the malicious metadata to the configuration directory, effectively overwriting the existing legitimate file.\nOnce the metadata is replaced, the plugin's SAML validation logic—which relies on the integrity of this file to verify identity assertions—is compromised. The attacker can then supply a maliciously crafted SAML assertion signed with their own keys, which the plugin will validate against the malicious metadata, leading to the successful authentication of the attacker as an arbitrary user identity.\nThe impact is total authorization bypass. By masquerading as a high-privileged user, the attacker gains full control over the Jenkins instance, including the ability to execute arbitrary commands through build scripts, exfiltrate sensitive credentials, and modify project configurations.\nThis vulnerability is particularly dangerous as it operates at the authentication layer, bypassing the necessity for valid credentials or existing session tokens. The attack does not require authentication to the target instance, and it is accessible via standard network exposure to the Jenkins web interface.\nThe issue persists across all versions of the Jenkins SAML Plugin up to and including 4.618.v441a_27fa_46d2, highlighting a structural weakness in how the plugin manages external configuration files via the Stapler framework."
}