CVE-2026-33001: 
Java vulnerability analysis and mitigation

CVE-2026-33001 is a link-following vulnerability in Jenkins core that allows arbitrary file creation and potential code execution through crafted .tar and .tar.gz archives. It affects Jenkins weekly releases up to and including 2.554, and LTS releases up to and including 2.541.2. The vulnerability was disclosed on March 18, 2026, via the Jenkins Security Advisory (SECURITY-3657), and was reported through the Jenkins Bug Bounty Program sponsored by the European Commission. It carries a CVSS v3.1 base score of 8.8 (High) (Jenkins Advisory, Feedly).

The root cause is improper handling of symbolic links during archive extraction (CWE-22: Path Traversal; CWE-59: Improper Link Resolution Before File Access). When Jenkins extracts .tar or .tar.gz archives, it does not validate whether symlinks within the archive resolve to paths outside the intended extraction directory, enabling a "zip slip"-style attack via symlink following. An attacker with Item/Configure permission, or the ability to control agent processes, can craft a malicious archive that writes files to arbitrary locations on the controller filesystem — limited only by the OS-level permissions of the Jenkins process user. Prominent affected features include the "Archive the artifacts" post-build action and the archiveArtifacts/archive Pipeline steps when using the standard artifact manager (Jenkins Advisory, Red Hat Bugzilla).

Successful exploitation allows an attacker to write arbitrary files to the Jenkins controller filesystem, constrained only by the file system permissions of the Jenkins process user. Critical attack scenarios include writing malicious Groovy scripts to JENKINS_HOME/init.groovy.d/ (which execute on Jenkins startup) or deploying rogue plugins to JENKINS_HOME/plugins/, both resulting in remote code execution on the controller. This threatens full confidentiality, integrity, and availability of the Jenkins controller and, by extension, any CI/CD pipelines and secrets it manages (Jenkins Advisory, Feedly).

No public proof-of-concept exploit code has been identified, and there is no evidence of in-the-wild exploitation at this time. The EPSS score is approximately 0.005% (very low probability of near-term exploitation). The vulnerability is not currently listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. However, the low privilege requirement (Item/Configure permission or agent control) and network-accessible attack vector make it a meaningful risk in multi-tenant or shared Jenkins environments (Feedly, Jenkins Advisory).

1. Reconnaissance: Identify a Jenkins instance running weekly version ≤ 2.554 or LTS ≤ 2.541.2. Confirm the attacker has Item/Configure permission on at least one job, or has the ability to control an agent process.
2. Craft malicious archive: Create a .tar or .tar.gz archive containing a symlink that points outside the intended extraction directory (e.g., a symlink named link pointing to ../../../../JENKINS_HOME/init.groovy.d/) and a payload file (e.g., a malicious Groovy script) placed at link/evil.groovy.
3. Upload via artifact archiving: Configure a Jenkins job to archive artifacts using the "Archive the artifacts" post-build action or archiveArtifacts Pipeline step. Trigger a build that produces or includes the crafted archive as an artifact.
4. Trigger extraction: Cause Jenkins to extract the malicious archive on the controller (e.g., by using a downstream job or pipeline step that retrieves and unpacks the artifact on the controller filesystem).
5. Achieve code execution: The symlink causes the payload Groovy script to be written to JENKINS_HOME/init.groovy.d/. Upon the next Jenkins restart (or if the directory is polled), the script executes with the privileges of the Jenkins process, enabling reverse shell, credential theft, or further lateral movement (Jenkins Advisory, Red Hat Bugzilla).

• File System: Unexpected files in JENKINS_HOME/init.groovy.d/ or JENKINS_HOME/plugins/ not corresponding to legitimate administrator actions; presence of symlinks within artifact staging directories pointing outside the workspace.
• Logs: Jenkins build logs showing artifact archiving steps involving .tar or .tar.gz files from untrusted or agent-controlled sources; Jenkins system logs recording unexpected plugin loads or Groovy script executions at startup.
• Process: Unusual child processes spawned by the Jenkins JVM (e.g., bash, curl, wget, python) following a Jenkins restart; unexpected outbound network connections from the Jenkins controller.
• Network: Outbound connections from the Jenkins controller to unknown external IPs shortly after a build involving artifact archiving completes.

Jenkins has released patched versions that address this vulnerability: Jenkins weekly 2.555 and Jenkins LTS 2.541.3. The fix causes Jenkins to refuse extraction of files from .tar/.tar.gz archives whose resolved path falls outside the target directory, and blocks extraction through symbolic links in the path or at the target location. Administrators unable to upgrade immediately should restrict Item/Configure permissions to trusted users only, limit agent process control to trusted operators, and monitor JENKINS_HOME/init.groovy.d/ and JENKINS_HOME/plugins/ for unauthorized changes (Jenkins Advisory).

The vulnerability received coverage from multiple cybersecurity news outlets including GBHackers, CyberPress, CyberSecurityNews, and SecurityOnline, which highlighted it alongside other critical Jenkins CVEs disclosed in the same advisory. The Hacker News included it in their weekly CI/CD security recap. Multiple independent researchers were credited with discovering the issue, including researchers from Airbus Protect Offensive Security Team and Cato Networks, reflecting broad community attention to Jenkins supply chain security risks (SecurityOnline, The Hacker News, Jenkins Advisory).