CVE-2026-42521

// Conceptual PoC demonstrating the configuration modification // This is not a direct exploit script but shows the vulnerable mechanism. // Attacker modifies the configuration XML (e.g., config.xml) to include: // <inheritanceStrategy class="java.io.File"/> // or a class available on the classpath that performs a sensitive action in its constructor. // Example Groovy script to simulate the vulnerable instantiation: try { // The vulnerable code effectively does this: def clazz = Class.forName("java.io.File"); // Arbitrary class def instance = clazz.getConstructor().newInstance("/etc/passwd"); // If constructor requires args, it might fail, but parameterless constructors are the target. // Real exploitation relies on finding a parameterless constructor that does something dangerous. // e.g., a logging class that dumps context, or a utility class that initializes system properties. println("Instance created: " + instance.getClass().getName()); } catch (Exception e) { e.printStackTrace(); }

{"cve": {"id": "CVE-2026-42521", "sourceIdentifier": "[email protected]", "published": "2026-04-29T14:16:19.170", "lastModified": "2026-05-06T16:21:01.660", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Jenkins Matrix Authorization Strategy Plugin 2.0-beta-1 through 3.2.9 (both inclusive) invokes parameterless constructors of classes specified in configuration when deserializing inheritance strategies, without restricting the classes that can be instantiated, allowing attackers with Item/Configure permission to instantiate arbitrary types, which may lead to information disclosure or other impacts depending on the classes available on the classpath."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N", "baseScore": 6.5, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-502"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:jenkins:matrix_authorization_strategy:*:*:*:*:*:jenkins:*:*", "versionStartIncluding": "2.1", "versionEndExcluding": "3.2.10", "matchCriteriaId": "E3A25BA3-0771-4973-A265-27CCD8973FD5"}, {"vulnerable": true, "criteria": "cpe:2.3:a:jenkins:matrix_authorization_strategy:2.0:beta1:*:*:*:jenkins:*:*", "matchCriteriaId": "5BE52D85-98B6-42EF-8817-A0039B61406A"}, {"vulnerable": true, "criteria": "cpe:2.3:a:jenkins:matrix_authorization_strategy:2.0:beta2:*:*:*:jenkins:*:*", "matchCriteriaId": "55E2BB1C-F686-46E0-8D12-A0C70DF2CC91"}, {"vulnerable": true, "criteria": "cpe:2.3:a:jenkins:matrix_authorization_strategy:2.0:beta3:*:*:*:jenkins:*:*", "matchCriteriaId": "B5E7F6EB-50E0-4A3B-A481-45BD14714558"}]}]}], "references": [{"url": "https://www.jenkins.io/security/advisory/2026-04-29/#SECURITY-3676", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}