CVE-2026-48919 Overview
CVE-2026-48919 affects the Jenkins Active Directory Plugin versions 2.41 and earlier. The plugin deserializes data returned from Lightweight Directory Access Protocol (LDAP) referrals without validation. An attacker who can influence LDAP referral responses can deliver crafted serialized Java objects to the Jenkins controller. Successful exploitation leads to insecure deserialization [CWE-502], which can compromise the confidentiality, integrity, and availability of the Jenkins environment. The vulnerability requires high attack complexity and high privileges, limiting opportunistic exploitation but remaining relevant for environments where attackers control or intercept LDAP infrastructure.
Critical Impact
Unvalidated deserialization of LDAP referral data in the Jenkins Active Directory Plugin can enable arbitrary object instantiation against the Jenkins controller.
Affected Products
- Jenkins Active Directory Plugin version 2.41
- Jenkins Active Directory Plugin versions earlier than 2.41
- Jenkins controllers configured to authenticate against Active Directory using the affected plugin
Discovery Timeline
- 2026-05-27 - CVE-2026-48919 published to the National Vulnerability Database
- 2026-05-27 - Jenkins published Security Advisory SECURITY-3659
- 2026-05-27 - Last updated in NVD database
Technical Details for CVE-2026-48919
Vulnerability Analysis
The Jenkins Active Directory Plugin integrates Jenkins authentication with Microsoft Active Directory through LDAP queries. When the plugin processes responses from the directory service, it follows LDAP referrals that point clients to alternate servers for additional data. In affected versions, the plugin deserializes attributes returned by referral responses without validating the source or content of the serialized payload.
Insecure deserialization in Java contexts allows the construction of gadget chains. These chains abuse existing classes on the classpath to execute attacker-controlled behavior during object reconstruction. Jenkins controllers typically include many libraries that expose viable gadget chains.
Root Cause
The root cause is the absence of validation around objects returned by LDAP referrals [CWE-502]. The plugin trusts the referral endpoint to return safe data and invokes Java deserialization on attacker-influenceable input. This violates the principle that deserialization must occur only on data from trusted, integrity-protected sources.
Attack Vector
Exploitation requires an attacker positioned to influence LDAP referral responses received by the Jenkins controller. This typically means controlling a rogue LDAP server, performing a network-level interception, or operating a malicious referral target reachable from the Jenkins controller. The CVSS vector indicates network-based access, high attack complexity, and the need for high privileges. Successful exploitation can yield arbitrary object instantiation and, depending on available gadgets, code execution within the Jenkins process. Refer to the Jenkins Security Advisory SECURITY-3659 for vendor-confirmed technical details.
Detection Methods for CVE-2026-48919
Indicators of Compromise
- Unexpected outbound LDAP or LDAPS connections from Jenkins controllers to hosts outside the configured directory infrastructure
- Jenkins controller logs showing LDAP referral processing followed by Java deserialization stack traces or ClassNotFoundException entries
- Spawning of child processes by the Jenkins controller JVM that do not correspond to normal build agents
Detection Strategies
- Inventory all Jenkins instances and identify Active Directory Plugin versions at or below 2.41
- Inspect Jenkins audit logs for authentication attempts that triggered referral chasing to unfamiliar domain controllers
- Correlate LDAP traffic with process telemetry on the Jenkins host to surface deserialization-driven command execution
Monitoring Recommendations
- Alert on Jenkins controller processes executing shells, scripting interpreters, or network utilities outside expected build workflows
- Monitor egress LDAP traffic from CI/CD infrastructure and restrict it to known directory servers
- Track plugin version drift across the Jenkins fleet to detect instances that miss security updates
How to Mitigate CVE-2026-48919
Immediate Actions Required
- Upgrade the Jenkins Active Directory Plugin to the fixed release referenced in Jenkins Security Advisory SECURITY-3659
- Restrict Jenkins controller egress so that LDAP and LDAPS traffic can only reach authorized domain controllers
- Review administrative accounts on Jenkins, since exploitation requires high privileges that may already be compromised
Patch Information
Jenkins addressed the issue in a fixed release of the Active Directory Plugin published alongside Security Advisory SECURITY-3659 on 2026-05-27. Administrators should apply the update through the Jenkins Plugin Manager and restart the controller. Consult the advisory for the exact fixed version and any configuration changes recommended by the maintainers.
Workarounds
- Disable LDAP referral chasing in the Active Directory Plugin configuration where operationally feasible
- Place Jenkins controllers behind network segmentation that prevents reaching arbitrary referral targets
- Limit accounts able to modify Jenkins security realm configuration to reduce the attack surface for high-privilege exploitation
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
