High

Jenkins CLI WebSocket Origin Validation Bypass via DNS Rebinding

IdentifiersCVE-2026-33002CWE-346

CVE-2026-33002 is a high-severity origin validation flaw in the Jenkins CLI WebSocket endpoint affecting Jenkins 2.442 through 2.554 and Jenkins LTS 2.426.3 through 2.541.2. Jenkins introduced origin validation for the CLI WebSocket endpoint to prevent cross-site WebSocket hijacking, but in affected versions it computed the expected origin using the untrusted Host or X-Forwarded-Host HTTP request headers. Because these headers can be influenced in a DNS rebinding scenario, an attacker can bypass the origin check and establish a WebSocket connection to the Jenkins CLI endpoint from an attacker-controlled web origin. The issue affects deployments where the CLI WebSocket endpoint is available, particularly common Jetty-based Jenkins deployments such as native installers, packages, Docker containers, and java -jar jenkins.war. Successful exploitation allows the attacker to interact with the Jenkins CLI as the anonymous user and execute CLI commands permitted to that security context.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

The primary impact is unauthorized access to the Jenkins CLI over WebSocket by bypassing origin validation. This enables execution of CLI commands as the anonymous user. Impact depends heavily on the permissions granted to anonymous users: in hardened deployments with no anonymous permissions, exposure may be limited to low-value commands such as who-am-i and minor information disclosure; in insecure deployments where anonymous users retain broader permissions, the attacker may execute more powerful CLI commands. Under permissive authorization configurations such as "Anyone can do anything," the flaw can enable Groovy or groovysh CLI command execution and result in arbitrary code execution on the Jenkins controller. The vulnerability is especially concerning for Jenkins controllers on private networks because DNS rebinding can bridge a victim browser to an otherwise non-public target.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, enforce strict authentication and remove all permissions from the anonymous user to reduce the value of a successful bypass. Prefer HTTPS over plain HTTP, as the available information states exploitation requires HTTP rather than HTTPS. Restrict or disable access to the CLI WebSocket endpoint where operationally feasible, and limit browser access from untrusted sites for users who can reach the Jenkins controller. Review authorization strategies and eliminate permissive anonymous access, especially configurations equivalent to "Anyone can do anything."

Remediation

Patch, then assume compromise.

Upgrade Jenkins to 2.555 or Jenkins LTS to 2.541.3 or later, which contain the fix for CVE-2026-33002. Ensure all affected controllers, including packaged, containerized, and standalone war deployments, are updated. Review reverse-proxy behavior if X-Forwarded-Host is in use and confirm the deployment is operating on a supported fixed release.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

JenkinsJenkinsapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

6 SOURCESView more in app

cyber security newsNews

Mar 20, 2026

Critical Jenkins Vulnerabilities Expose CI/CD Servers to RCE Attacks

A high-severity DNS rebinding vulnerability in Jenkins WebSocket CLI origin validation that can allow unauthorized CLI access and potentially remote code execution under certain configurations.

What this page doesn’t show

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity4

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES

MITRE CVE

cve.org · CVE-2026-33002

NVD

nvd.nist.gov/vuln/detail/CVE-2026-33002

MITRE CWE · CWE-346

cwe.mitre.org

Vendor Advisory

jenkins.io/security/advisory/2026-03-18

Jenkins CLI WebSocket Origin Validation Bypass via DNS Rebinding

IdentifiersCVE-2026-33002CWE-346