CVE-2026-48916: Jenkins LDAP Plugin Information Vulnerability

CVE-2026-48916 Overview

CVE-2026-48916 affects the Jenkins LDAP Plugin version 807.v7d7de30930cf and earlier. The plugin follows Lightweight Directory Access Protocol (LDAP) referrals returned by directory servers without restriction. Following untrusted referrals can redirect authentication or directory queries to attacker-controlled LDAP servers. This behavior maps to Server-Side Request Forgery [CWE-918] because the Jenkins controller initiates outbound requests to attacker-chosen destinations.

Critical Impact

An attacker who controls or influences an LDAP response can redirect Jenkins LDAP queries to a malicious server, enabling credential capture or directory data exfiltration during authentication and group lookups.

Affected Products

• Jenkins LDAP Plugin 807.v7d7de30930cf and earlier

Discovery Timeline

• 2026-05-27 - CVE-2026-48916 published to NVD via Jenkins Security Advisory SECURITY-3654
• 2026-05-27 - Last updated in NVD database

Technical Details for CVE-2026-48916

Vulnerability Analysis

The Jenkins LDAP Plugin processes LDAP referrals returned by upstream directory servers. A referral instructs the LDAP client to redirect its query to another server identified by URL. The plugin follows these referrals automatically, without validating the destination against an allow list.

When a Jenkins controller binds to LDAP during user authentication or group resolution, a malicious or compromised LDAP server can respond with a referral pointing to an attacker-controlled host. The Jenkins client then re-sends the bind operation, including the supplied credentials, to that destination. This is a Server-Side Request Forgery condition because the Jenkins server makes outbound network requests on behalf of an attacker.

Exploitation requires either control of the configured LDAP server, a man-in-the-middle position on the LDAP channel, or write access sufficient to inject referral entries into the directory tree. The advisory characterizes the attack complexity as high and requires elevated privileges, which constrains practical exploitation.

Root Cause

The root cause is insecure default handling of LDAP referrals. The plugin uses the JNDI default behavior of following referrals (java.naming.referral=follow) without enforcing a destination policy. No validation restricts the referral target to trusted hosts.

Attack Vector

The attack vector is network-based. An attacker with control over LDAP responses returns a referral pointing to a rogue LDAP server. When Jenkins re-issues the operation, credentials and directory queries flow to the attacker. See the Jenkins Security Advisory SECURITY-3654 for vendor-supplied technical details.

Detection Methods for CVE-2026-48916

Indicators of Compromise

• Outbound LDAP or LDAPS connections from the Jenkins controller to hosts not listed in the configured LDAP server URL.
• Unexpected DNS resolutions for hostnames embedded in LDAP referral URLs originating from the Jenkins host.
• Authentication failures or repeated bind attempts in Jenkins logs immediately following successful directory queries.

Detection Strategies

• Inspect Jenkins LDAP Plugin version using Manage Jenkins → Plugins and flag installations at or below 807.v7d7de30930cf.
• Monitor network egress on TCP 389 and 636 from Jenkins controllers and alert on destinations outside an approved allow list.
• Review the Jenkins LDAP configuration for the referral handling setting and identify deployments where referrals are followed.

Monitoring Recommendations

• Forward Jenkins system logs and network flow data to a centralized analytics platform for correlation of LDAP bind events with outbound connections.
• Establish a baseline of expected LDAP server destinations and alert on deviations.
• Track plugin inventory changes through configuration-as-code or audit logs to detect downgrades to vulnerable versions.

How to Mitigate CVE-2026-48916

Immediate Actions Required

• Upgrade the Jenkins LDAP Plugin to the fixed version published in Jenkins Security Advisory SECURITY-3654.
• Restrict outbound LDAP traffic from Jenkins controllers to known directory servers using host or network firewalls.
• Audit Jenkins LDAP security realm configuration and confirm the directory server endpoint is authoritative and trusted.

Patch Information

Apply the patched Jenkins LDAP Plugin version referenced in the Jenkins Security Advisory SECURITY-3654. Updated plugins are available through the Jenkins Update Center.

Workarounds

• Disable LDAP referral following in the JNDI environment used by the plugin where configuration permits.
• Enforce LDAPS with strict certificate validation to prevent referral injection from a man-in-the-middle position.
• Segment the Jenkins controller network to permit egress only to the sanctioned directory server IP addresses.

# Restrict Jenkins controller egress to a single LDAP server (example using iptables)
iptables -A OUTPUT -p tcp -d 10.0.0.10 --dport 636 -j ACCEPT
iptables -A OUTPUT -p tcp --dport 389 -j REJECT
iptables -A OUTPUT -p tcp --dport 636 -j REJECT