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The CVE-2026-48919 vulnerability resides in the Jenkins Active Directory Plugin (version 2.41 and prior) due to how it handles LDAP referrals. When configured to use an Active Directory server for authentication, the plugin can be instructed to follow an LDAP referral. An attacker capable of controlling the targeted AD server, or performing a man-in-the-middle (MitM) attack, can embed a specially crafted referral that points to a Remote Method Invocation (RMI) URL. The Jenkins controller then follows this referral and processes the returned RMI object. The plugin fails to validate this data before deserialization. If a suitable deserialization “gadget chain” (like those found in the popular `ysoserial` tool) is present on Jenkins’ classpath, the attacker can achieve Remote Code Execution (RCE). This attack abuses the Java Naming and Directory Interface (JNDI) and LDAP referral mechanism to deliver a malicious serialized payload, ultimately compromising the Jenkins controller.
DailyCVE Form:
Platform: Jenkins
Version: <=2.41
Vulnerability : Deserialization
Severity: Medium
date: 2026-05-27
Prediction: 2026-06-10
What Undercode Say:
Check current plugin version
ls $JENKINS_HOME/plugins/active-directory.jpi
unzip -p $JENKINS_HOME/plugins/active-directory.jpi META-INF/MANIFEST.MF | grep Plugin-Version
Apply Mitigation (System Property)
echo "JAVA_OPTS=\"-Dhudson.plugins.active_directory.referral.ignore=true\"" >> /etc/default/jenkins
systemctl restart jenkins
Alternative: Patch using Jenkins Script Console
println("Ignoring referrals: " + System.setProperty("hudson.plugins.active_directory.referral.ignore", "true"));
Exploit:
- Control Resource: The attacker must control the Active Directory server or execute a MitM attack.
- Inject Payload: The attacker configures the AD/LDAP server to return a referral pointing to a malicious RMI server (
ldap://evil.com:1389/Exploit). - Trigger Deserialization: The Jenkins controller follows the referral, contacts the RMI server, and receives a serialized Java object.
- Achieve RCE: Jenkins deserializes the untrusted data. A `ysoserial` payload (e.g.,
CommonsCollections1) executes arbitrary commands on the controller.
Protection:
- Update Plugin: Upgrade to Active Directory Plugin version 2.41.1 or higher.
2. Mitigation: If update is impossible, set `-Dhudson.plugins.active_directory.referral.ignore=true`.
- Network Controls: Restrict Jenkins access to prevent MitM attacks (e.g., enforce LDAPS).
- General Hardening: Keep Jenkins core and all plugins up-to-date.
Impact:
Outcome: Full compromise of the Jenkins controller.
Privilege: Complete control over build pipelines, credentials, and stored secrets.
Supply Chain: Attackers can inject malicious code into build artifacts, poisoning the supply chain.
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Sources:
Reported By: nvd.nist.gov
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