CVE-2026-42523

Critical

Published: 29 April 2026

Published

29 April 2026

Modified

05 May 2026

KEV Added

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Patch

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CVSS Score 9.0 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H

EPSS Score 0.0004 12.9th percentile

Risk Priority 18 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-42523 is a critical-severity Cross-site Scripting (CWE-79) vulnerability in Jenkins Github. Its CVSS base score is 9.0 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 12.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-15 (Information Output Filtering).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match

prevent

SI-2 requires timely flaw remediation, directly addressing the specific stored XSS vulnerability in the Jenkins GitHub Plugin by mandating identification, reporting, and patching of the improper job URL processing.

SI-10 Information Input Validation good match

prevent

SI-10 enforces validation of information inputs such as the job URL, preventing injection of malicious JavaScript payloads that enable the stored XSS exploitation.

SI-15 Information Output Filtering good match

prevent

SI-15 mandates filtering of information output on job configuration pages, blocking execution of stored malicious JavaScript in users' browsers.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1059.007 JavaScript Execution

Adversaries may abuse various implementations of JavaScript for execution.

attack.mitre.org →

Why these techniques?

Stored XSS vulnerability in public-facing Jenkins plugin directly enables exploitation of the application (T1190) and facilitates arbitrary JavaScript execution in victim browsers (T1059.007).

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

Jenkins GitHub Plugin 1.46.0 and earlier improperly processes the current job URL as part of JavaScript implementing validation of the feature "GitHub hook trigger for GITScm polling", resulting in a stored cross-site scripting (XSS) vulnerability exploitable by non-anonymous attackers with…

Overall/Read permission.

Deeper analysisAI

CVE-2026-42523 is a stored cross-site scripting (XSS) vulnerability, mapped to CWE-79, affecting Jenkins GitHub Plugin versions 1.46.0 and earlier. The flaw occurs when the plugin improperly processes the current job URL as part of JavaScript code implementing validation for the "GitHub hook trigger for GITScm polling" feature. Published on 2026-04-29, it carries a CVSS v3.1 base score of 9.0 (AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H), reflecting critical severity due to network accessibility, low attack complexity, and potential for high impacts across confidentiality, integrity, and availability with scope change.

Non-anonymous attackers possessing Overall/Read permission can exploit this stored XSS vulnerability. By injecting malicious payloads via the job URL during plugin interactions, they can store executable JavaScript that triggers in the browsers of other users viewing the affected job configuration, requiring user interaction but enabling broad compromise within the Jenkins instance.

The official Jenkins security advisory at https://www.jenkins.io/security/advisory/2026-04-29/#SECURITY-3704 provides guidance on mitigation and patching for this issue.