# CVE-2026-77607: Semantic MediaWiki affected by Special:Ask table `sep` parameter reflected XSS

> CVE-2026-77607 (GitHub advisory GHSA-7xv3-gf2g-498h) is a medium-severity vulnerability with a CVSS 3.1 base score of 6.1, classed as Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (CWE-79), in mediawiki/semantic-media-wiki (Packagist). Affected versions: <= 7.1.0. It is fixed in 7.2.0.

Canonical page: https://cveminer.com/vulnerabilities/CVE-2026-77607

| Field | Value |
| --- | --- |
| CVE | CVE-2026-77607 |
| GHSA | GHSA-7xv3-gf2g-498h |
| Severity | Medium |
| CVSS 3.1 | 6.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N` (GitHub Advisory Database) |
| CWE | CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') |
| EPSS | 0.15% (higher than 5% of CVEs) |
| CISA KEV | Not listed |
| SSVC | exploitation none, automatable no, technical impact partial |
| Published | 18 Sept 2026 |
| Modified | 18 Sept 2026 |

## Description

###### Failure mode

`sep` was inserted verbatim into the HTML that joins a table cell's values. This made it possible to inject HTML through the separator value. The same unsanitised table HTML is produced both for the standard `Special:Ask` render and for its raw request output (`request_type=raw`), so the injection was reachable without authentication.

###### Remediation

- In all non-wiki output modes (HTML, raw request, file), `sep` is escaped unless it is a safe `<br>` variant.
- This preserves legitimate line-break separators while blocking markup injection.

###### Maintenance note

If the table renderer ever gains richer separator semantics, keep the whitelist explicit. Do not expand the allowed HTML surface casually.

## Affected packages

| Package | Ecosystem | PURL | Vulnerable versions | Fixed in |
| --- | --- | --- | --- | --- |
| mediawiki/semantic-media-wiki | Packagist | `pkg:composer/mediawiki/semantic-media-wiki` | <= 7.1.0 | 7.2.0 |

## Fix commits

- Release: https://github.com/semanticmediawiki/semanticmediawiki/commit/0d11c070bbe64f4425e3ab8be89eefa926dd9e4e (7.2.0)

## Questions

**What is the GHSA ID for CVE-2026-77607?**

GitHub tracks CVE-2026-77607 as GHSA-7xv3-gf2g-498h.

**What is the CVSS score of CVE-2026-77607?**

CVE-2026-77607 has a CVSS 3.1 base score of 6.1 (Medium), vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

**Which versions are affected by CVE-2026-77607?**

mediawiki/semantic-media-wiki (Packagist): <= 7.1.0.

**How do I fix CVE-2026-77607?**

Upgrade to 7.2.0 or later.

**What is the Package URL (PURL) for CVE-2026-77607?**

The affected package's PURL is pkg:composer/mediawiki/semantic-media-wiki.

**Is CVE-2026-77607 exploited in the wild?**

CISA's Known Exploited Vulnerabilities catalog doesn't list CVE-2026-77607. That means no confirmed exploitation has been catalogued, not that it is safe to leave unpatched. CISA's SSVC assessment rates exploitation as "none". EPSS estimates a 0.15% chance of exploitation in the next 30 days, higher than 5% of CVEs.

## References

- https://github.com/SemanticMediaWiki/SemanticMediaWiki/security/advisories/GHSA-7xv3-gf2g-498h (advisory)
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/77xxx/CVE-2026-77607.json (advisory)
- https://nvd.nist.gov/vuln/detail/CVE-2026-77607 (advisory)
- https://github.com/advisories/GHSA-7xv3-gf2g-498h (advisory)
- https://github.com/SemanticMediaWiki/SemanticMediaWiki (package)
- https://github.com/SemanticMediaWiki/SemanticMediaWiki/releases/tag/7.2.0

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Source: CVEminer (https://cveminer.com/vulnerabilities/CVE-2026-77607), compiled from OSV (GitHub advisory), GitHub Advisory Database, OSV (CVE record), CVE.org, CISA KEV catalog. OSV and GitHub Advisory Database content is licensed CC BY 4.0.