CVE-2026-42522 Overview
A missing permission check vulnerability exists in Jenkins GitHub Branch Source Plugin version 1967.vdea_d580c1a_b_a_ and earlier. This security flaw allows attackers with Overall/Read permission to connect to an attacker-specified URL using attacker-specified GitHub App credentials, potentially leading to credential abuse and Server-Side Request Forgery (SSRF) attacks.
Critical Impact
Attackers with minimal Jenkins permissions can abuse GitHub App credentials to establish connections to arbitrary URLs, potentially exposing sensitive credentials and enabling lateral movement within connected infrastructure.
Affected Products
- Jenkins GitHub Branch Source Plugin version 1967.vdea_d580c1a_b_a_ and earlier
Discovery Timeline
- April 29, 2026 - CVE-2026-42522 published to NVD
- April 29, 2026 - Last updated in NVD database
Technical Details for CVE-2026-42522
Vulnerability Analysis
This vulnerability is classified under CWE-862 (Missing Authorization), which occurs when a software component does not perform an authorization check when an actor attempts to access a resource or perform an action. In this case, the Jenkins GitHub Branch Source Plugin fails to properly validate user permissions before allowing connections to external URLs with configured GitHub App credentials.
The vulnerability enables a network-based attack that can be exploited by any authenticated user with the Overall/Read permission level in Jenkins. This is a relatively low barrier to exploitation since Overall/Read is a common permission granted to many Jenkins users. The attack requires no user interaction and can be executed remotely, making it accessible to any user with basic Jenkins access.
Root Cause
The root cause is a missing permission check in the plugin's endpoint handling code. When the plugin processes requests to connect to external URLs using GitHub App credentials, it only verifies that the user has Overall/Read permission but fails to check for more restrictive permissions that should be required for credential usage and external connection initiation.
This authorization gap allows users who should only have read access to Jenkins configuration to abuse credential functionality that should be restricted to administrators or users with explicit credential management permissions.
Attack Vector
An attacker with Overall/Read permission in Jenkins can exploit this vulnerability by:
- Identifying the vulnerable GitHub Branch Source Plugin endpoint
- Crafting a request that specifies an attacker-controlled URL as the connection target
- Including attacker-specified GitHub App credentials in the request
- Triggering the connection, which the server executes without proper authorization checks
This can lead to credential theft if the attacker can capture the GitHub App credentials in transit, or can be used to perform SSRF attacks against internal infrastructure that the Jenkins server can reach.
The vulnerability is exploited through malicious API requests to the Jenkins plugin endpoint. See the Jenkins Security Advisory #2026-04-29 for complete technical details on the affected endpoints and exploitation vectors.
Detection Methods for CVE-2026-42522
Indicators of Compromise
- Unusual outbound connection attempts from Jenkins servers to unexpected external URLs
- Jenkins audit logs showing credential access by users with only Overall/Read permissions
- Connection attempts to internal network resources from the Jenkins server that don't match normal pipeline behavior
- GitHub App credential usage patterns that deviate from established baselines
Detection Strategies
- Monitor Jenkins access logs for requests to GitHub Branch Source Plugin endpoints from users without administrative privileges
- Implement network monitoring to detect Jenkins server connections to non-whitelisted external URLs
- Review Jenkins audit trails for unauthorized credential access attempts
- Deploy Web Application Firewall (WAF) rules to detect and block suspicious requests to Jenkins plugin endpoints
Monitoring Recommendations
- Enable verbose logging for the GitHub Branch Source Plugin to capture all connection attempts
- Configure alerts for GitHub App credential usage outside of normal CI/CD pipeline operations
- Implement network segmentation monitoring to detect SSRF attempts from Jenkins servers
- Set up real-time monitoring for Jenkins authentication and authorization events
How to Mitigate CVE-2026-42522
Immediate Actions Required
- Update Jenkins GitHub Branch Source Plugin to the latest patched version immediately
- Review and restrict Overall/Read permissions to only necessary users
- Audit Jenkins access logs for any suspicious activity that may indicate prior exploitation
- Temporarily disable the GitHub Branch Source Plugin if immediate patching is not possible
Patch Information
Jenkins has released a security advisory addressing this vulnerability. Administrators should update to the latest version of the GitHub Branch Source Plugin as documented in the Jenkins Security Advisory #2026-04-29. The update includes proper permission checks for credential-related operations.
Workarounds
- Restrict Overall/Read permission to only trusted users who require Jenkins access
- Implement network-level controls to limit outbound connections from Jenkins servers to approved destinations only
- Use Jenkins Role-Based Access Control (RBAC) to implement more granular permission controls
- Monitor and alert on any GitHub Branch Source Plugin endpoint access until the patch can be applied
# Example: Review current plugin version in Jenkins CLI
java -jar jenkins-cli.jar -s http://your-jenkins-server/ list-plugins | grep github-branch-source
# Example: Update plugin via CLI
java -jar jenkins-cli.jar -s http://your-jenkins-server/ install-plugin github-branch-source -deploy
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
