CVE-2017-1000085 in Jenkins
Summary
by MITRE
Subversion Plugin connects to a user-specified Subversion repository as part of form validation (e.g. to retrieve a list of tags). This functionality improperly checked permissions, allowing any user with Item/Build permission (but not Item/Configure) to connect to any web server or Subversion server and send credentials with a known ID, thereby possibly capturing them. Additionally, this functionality did not require POST requests be used, thereby allowing the above to be performed without direct access to Jenkins via Cross-Site Request Forgery attacks.
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Analysis
by VulDB Data Team • 11/21/2019
The vulnerability identified as CVE-2017-1000085 affects the Subversion plugin within Jenkins continuous integration system, presenting a significant security risk through improper permission handling during repository validation processes. This flaw exists in the plugin's form validation mechanism where it attempts to connect to user-specified Subversion repositories to retrieve information such as available tags. The issue stems from inadequate access control checks that fail to properly validate user privileges before establishing connections to external systems.
The technical implementation of this vulnerability allows attackers with minimal permissions to exploit the system's trust model. Specifically, users who possess Item/Build permissions but lack Item/Configure access can leverage this flaw to establish connections to any web server or Subversion server within the network. This permission bypass occurs because the plugin does not adequately verify whether the requesting user has appropriate authorization levels to access the target repository. The vulnerability creates a scenario where legitimate credentials can be captured and potentially misused by unauthorized parties.
The operational impact of this vulnerability extends beyond simple credential theft through the absence of proper request validation mechanisms. The plugin fails to enforce the use of POST requests for the validation functionality, which creates an avenue for exploitation through Cross-Site Request Forgery attacks. This means that an attacker could potentially trigger the vulnerable functionality without requiring direct access to the Jenkins instance, making the attack surface significantly larger and more accessible. The combination of weak permission checking and lack of CSRF protection creates a dangerous combination that allows for unauthorized system access and potential credential harvesting.
This vulnerability maps directly to CWE-284 which addresses improper access control issues, and aligns with ATT&CK technique T1566 related to credential access through exploitation of web application vulnerabilities. The flaw represents a classic case of insufficient authorization checks where the system fails to properly validate user privileges before performing sensitive operations. Organizations using Jenkins with the Subversion plugin should immediately implement mitigations including updating to patched versions of the plugin, implementing proper access controls, and configuring network-level restrictions to prevent unauthorized connections to external repositories. Additionally, enforcing the use of POST requests for all validation operations and implementing CSRF protection mechanisms would effectively mitigate this vulnerability's exploitation potential.