Jenkins GitHub Plugin Stored XSS via Job URL Validation

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.

Casky was already ahead

This CVE exploits attack patterns that Casky's 301matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.

Analysis

Jenkins GitHub Plugin versions 1.46.0 and earlier contain a stored cross-site scripting (XSS) vulnerability in the GitHub hook trigger validation feature. The vulnerability arises from improper processing of the current job URL within JavaScript code, allowing attackers with Overall/Read permissions to inject malicious scripts that persist in the Jenkins instance. This is particularly concerning because stored XSS vulnerabilities can compromise any user who views the affected Jenkins job, potentially leading to credential theft, lateral movement, or administrative takeover. Organizations running vulnerable Jenkins instances with GitHub integrations face significant risk, as the exploit requires only basic read access—a permission level commonly granted to developers and CI/CD users.

Casky's skill mapping identifies this vulnerability through detection patterns tied to MITRE ATT&CK techniques TA0001 (Initial Access) and TA0043 (Reconnaissance). When practitioners run Casky's 301 matched skills using Claude AI's extended reasoning capabilities, they will surface findings related to: (1) improper input validation in web application parameters, specifically detecting unsanitized URL strings reflected in JavaScript contexts; (2) script injection detection patterns that identify dynamic JavaScript generation without proper encoding; and (3) privilege escalation reconnaissance where low-permission users probe for XSS injection points. Practitioners will see alerts flagging instances where job URLs are processed client-side without HTML/JavaScript entity encoding, suspicious GitHub webhook payloads containing script tags, and audit logs showing non-anonymous users accessing job configuration pages—all indicators of exploitation attempts or successful payload delivery against this CVE.

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Casky Risk Score

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EPSS Probability

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Shodan Exposure

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GreyNoise Signal

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301 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-42523.

analyzing-apt-group-with-mitre-navigator

threat intelligence · low

Run

analyzing-campaign-attribution-evidence

threat intelligence · low

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analyzing-certificate-transparency-for-phishing

threat intelligence · low

Run

MITRE ATT&CK Techniques

TA0001 TA0043

Investigate the attack patterns behind CVE-2026-42523

Casky has 301 skills that investigate the attack patterns behind CVE-2026-42523. Run one and get CVSS-scored findings in 3 minutes.

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