# CVE-2026-126564: Semantic MediaWiki 2.5.0 before 7.4.1 Stored XSS via Special:Browse Factbox Title

Status: published. Published: 2026-11-11. Updated: 2026-11-12.

Semantic MediaWiki 2.5.0 before 7.4.1 contains a stored cross-site scripting vulnerability in ValueFormatter::getFormattedSubject() that renders property label segments after a literal   as unescaped markup. Users with page-edit rights can set a preferred property label containing an img onerror payload that executes when anyone, including administrators, views Special:Browse or the smwbrowse API.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/SemanticMediaWiki/SemanticMediaWiki/commit/c9bf9f25549bb2f5eab916339b267a1732002c4c

## Affected products and versions

- SemanticMediaWiki / SemanticMediaWiki (mediawiki/semantic-media-wiki): ≥ 2.5.0; < 7.4.1 (affected, semver); 7.4.1 (unaffected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 5.1 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 5.4 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N; source: CNA: VulnCheck

- CVSS 4.0: 5.1 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/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; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 5.4 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.22% as of 2026-11-12; percentile 13.10%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-79

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/SemanticMediaWiki/SemanticMediaWiki/security/advisories/GHSA-mc5x-2j7v-x8hp (CNA: VulnCheck; vendor-advisory)

- https://github.com/SemanticMediaWiki/SemanticMediaWiki/commit/c9bf9f25549bb2f5eab916339b267a1732002c4c (CNA: VulnCheck; patch)

- https://github.com/SemanticMediaWiki/SemanticMediaWiki/releases/tag/7.4.1 (CNA: VulnCheck; release-notes)

- https://github.com/SemanticMediaWiki/SemanticMediaWiki/blob/7.4.0/src/MediaWiki/Specials/Browse/ValueFormatter.php#L34-L55 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/semantic-mediawiki-2.5.0-before-7.4.1-stored-xss-via-special-browse-factbox-title (CNA: VulnCheck; third-party-advisory)

- https://github.com/SemanticMediaWiki/SemanticMediaWiki/blob/7.4.0/src/MediaWiki/Specials/Browse/ValueFormatter.php#L34-L55 (disclosure@vulncheck.com)

- https://github.com/SemanticMediaWiki/SemanticMediaWiki/commit/c9bf9f25549bb2f5eab916339b267a1732002c4c (disclosure@vulncheck.com)

- https://github.com/SemanticMediaWiki/SemanticMediaWiki/releases/tag/7.4.1 (disclosure@vulncheck.com)

- https://github.com/SemanticMediaWiki/SemanticMediaWiki/security/advisories/GHSA-mc5x-2j7v-x8hp (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/semantic-mediawiki-2.5.0-before-7.4.1-stored-xss-via-special-browse-factbox-title (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-126564; retrieved 2026-11-12; source updated 2026-11-12

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126564; retrieved 2026-11-11; source updated 2026-11-11

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-126564; retrieved 2026-11-12; source updated Not reported

Revision: 8fe3d491869cd72863f2e9974676c2e025566bef6055137a40d1f8121c38588f

Canonical: https://y2.dev/cve/CVE-2026-126564

## Agent and API access

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- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

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