CVE-2026-48917 Overview
CVE-2026-48917 affects the Jenkins LDAP Plugin version 807.v7d7de30930cf and earlier. The plugin deserializes data from Lightweight Directory Access Protocol (LDAP) referrals without validation. This insecure deserialization flaw [CWE-502] allows an attacker who controls an LDAP referral response to inject crafted serialized objects. When Jenkins processes the referral, the unvalidated object stream can lead to code execution within the Jenkins controller context.
Critical Impact
An attacker able to influence LDAP referrals can deserialize arbitrary objects, compromising confidentiality, integrity, and availability of the Jenkins controller.
Affected Products
- Jenkins LDAP Plugin 807.v7d7de30930cf and earlier
- Jenkins controllers using the LDAP security realm
- Build environments authenticating against LDAP directory services
Discovery Timeline
- 2026-05-27 - Jenkins publishes Security Advisory SECURITY-3654
- 2026-05-27 - CVE CVE-2026-48917 published to NVD
- 2026-05-27 - Last updated in NVD database
Technical Details for CVE-2026-48917
Vulnerability Analysis
The Jenkins LDAP Plugin handles LDAP referrals returned by directory servers during authentication and group lookup operations. The plugin deserializes data carried in these referrals without applying type filtering or other validation. An attacker who controls the LDAP server, or who can inject a malicious referral into the LDAP response chain, can supply a serialized Java object graph that triggers gadget chains on the Jenkins classpath.
Deserialization flaws of this class typically enable remote code execution when exploitable gadgets exist in the runtime. The attack requires high privileges and high attack complexity, which limits the population of exploiters but does not reduce the severity of a successful intrusion. Successful exploitation grants the attacker the same privileges as the Jenkins controller process.
Root Cause
The root cause is unsafe Java object deserialization on referral data returned by the LDAP server. The plugin trusts the serialized stream and does not enforce an allowlist of expected classes during object reconstruction. This violates the secure deserialization guidance encoded in [CWE-502].
Attack Vector
Exploitation occurs over the network. An attacker positions a malicious or compromised LDAP server, or injects a referral pointing to attacker-controlled infrastructure. When Jenkins follows the referral, the plugin reads the serialized payload and instantiates the embedded objects. Gadget chains present in the Jenkins controller or in installed plugins then drive arbitrary code execution. See the Jenkins Security Advisory SECURITY-3654 for vendor technical details.
Detection Methods for CVE-2026-48917
Indicators of Compromise
- Unexpected outbound LDAP connections from Jenkins controllers to untrusted hosts following referral chains
- Java deserialization errors or unusual class loading events in Jenkins logs during LDAP authentication
- New child processes spawned by the Jenkins controller JVM shortly after LDAP operations
Detection Strategies
- Inspect Jenkins controller logs for stack traces referencing ObjectInputStream, readObject, or LDAP referral handling during authentication events
- Monitor LDAP traffic for referral responses originating from servers outside the approved directory infrastructure
- Correlate authentication events in the LDAP plugin with anomalous process execution on the Jenkins host
Monitoring Recommendations
- Enable verbose logging on the Jenkins LDAP security realm and forward events to a centralized log platform
- Alert on Jenkins controller processes initiating shells, scripting interpreters, or outbound connections to non-corporate destinations
- Track plugin version inventory across Jenkins controllers to identify unpatched instances of the LDAP Plugin
How to Mitigate CVE-2026-48917
Immediate Actions Required
- Upgrade the Jenkins LDAP Plugin to the fixed release identified in Jenkins Security Advisory SECURITY-3654
- Restrict Jenkins controllers to authenticate only against trusted, internal LDAP servers
- Block outbound LDAP traffic from Jenkins controllers to untrusted networks at the firewall
Patch Information
Apply the fixed version of the Jenkins LDAP Plugin as published in the Jenkins Security Advisory dated 2026-05-27. The patch adds validation on data deserialized from LDAP referrals. Refer to the Jenkins Security Advisory SECURITY-3654 for the exact fixed version and upgrade instructions.
Workarounds
- Disable LDAP referral following in the Jenkins LDAP security realm configuration if the directory topology permits
- Limit administrative access to Jenkins to reduce the population of accounts capable of triggering LDAP operations
- Network-segment Jenkins controllers so that only approved LDAP endpoints are reachable
# Configuration example: verify installed Jenkins LDAP Plugin version
jenkins-plugin-cli --list | grep ldap
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
