CVE-2026-53439: Jenkins Information Disclosure Flaw

CVE-2026-53439 Overview

CVE-2026-53439 is a missing authorization vulnerability in Jenkins automation server. The flaw affects Jenkins 2.567 and earlier, and LTS releases 2.555.2 and earlier. Attackers with Overall/Read permission can determine other users' configured timezone. They can also enumerate view names from other users' "My Views" configurations. The vulnerability stems from absent permission checks on endpoints that return user-specific data. While the information exposure is limited, the issue enables reconnaissance against authenticated Jenkins users. The flaw is tracked under [CWE-862: Missing Authorization].

Critical Impact
Authenticated attackers with minimal Overall/Read permission can harvest timezone settings and private view names belonging to other Jenkins users, supporting targeted follow-on attacks.

Affected Products

Jenkins weekly releases 2.567 and earlier
Jenkins LTS releases 2.555.2 and earlier
Jenkins controller installations exposing the affected user endpoints

Discovery Timeline

2026-06-10 - Jenkins project publishes Security Advisory SECURITY-3713
2026-06-10 - CVE-2026-53439 published to NVD
2026-06-10 - Last updated in NVD database

Technical Details for CVE-2026-53439

Vulnerability Analysis

The vulnerability resides in Jenkins endpoints that expose user-specific configuration data. The affected code paths do not validate whether the requesting principal has permission to read another user's properties. A user holding only Overall/Read permission can query these endpoints and receive the target user's configured timezone and the names of personal views saved under "My Views". The disclosed data does not include view contents or job configurations. However, view names and timezone strings can reveal organizational structure, working hours, and naming conventions used internally. The issue is classified as [CWE-862: Missing Authorization].

Root Cause

The root cause is missing permission checks in handlers that serve per-user properties. Jenkins enforces granular permissions through the Authentication and ACL subsystems. The affected handlers query user property objects directly without invoking the appropriate checkPermission call against the target user object. Any authenticated user able to read the Jenkins UI inherits sufficient access to trigger the lookup.

Attack Vector

Exploitation requires network access to the Jenkins controller and a valid account with Overall/Read permission. The attacker issues HTTP requests against the user-specific endpoints, iterating over known or enumerated usernames. No user interaction is required from the victim. The Jenkins Security Advisory SECURITY-3713 documents the specific endpoints involved. Refer to the Jenkins Security Advisory 2026-06-10 for technical details on the affected request paths.

Detection Methods for CVE-2026-53439

Indicators of Compromise

Repeated HTTP requests from a single authenticated session targeting /user/<username>/ endpoints across many distinct usernames
Access log patterns showing sequential enumeration of user identifiers by a low-privilege account
Requests for user property data originating from accounts that do not typically interact with user configuration pages

Detection Strategies

Parse Jenkins access logs for high-volume GET requests against per-user URLs from accounts holding only Overall/Read
Establish a baseline of normal user-page access frequency and alert on statistical outliers
Correlate Jenkins authentication events with downstream requests touching multiple distinct user identifiers within a short window

Monitoring Recommendations

Forward Jenkins access.log and audit.log data to a centralized logging platform for retention and query
Enable the Jenkins Audit Trail plugin to capture authenticated request metadata
Review accounts with Overall/Read permission and validate they require that grant

How to Mitigate CVE-2026-53439

Immediate Actions Required

Upgrade Jenkins weekly to release 2.568 or later
Upgrade Jenkins LTS to release 2.555.3 or later
Audit users assigned Overall/Read permission and remove the grant where it is not required
Restrict network access to the Jenkins controller to trusted networks

Patch Information

The Jenkins project addressed CVE-2026-53439 in versions released alongside Security Advisory SECURITY-3713. The fix introduces the missing permission checks on the affected user property endpoints. Patch details are published in the Jenkins Security Advisory 2026-06-10. Administrators should apply the upgrade during the next maintenance window.

Workarounds

Remove Overall/Read permission from anonymous and authenticated user groups where feasible
Place the Jenkins controller behind an authenticating reverse proxy that restricts access to specific source networks
Disable or limit registration of new accounts pending upgrade

bash

# Configuration example - verify Jenkins version after upgrade
curl -s -u admin:$TOKEN https://jenkins.example.com/api/json | jq '.'
java -jar jenkins-cli.jar -s https://jenkins.example.com/ version