Nuxt MDC has an XSS vulnerability in markdown rendering that bypasses HTML filtering

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L

EPSS

• CVE-2025-54075: 0.34% estimated exploitation activity in the next 30 days; percentile 28.02 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A remote script-inclusion / stored XSS vulnerability in @nuxtjs/mdc lets a Markdown author inject a <base href="https://attacker.tld" element. The <base tag rewrites how all subsequent relative URLs are resolved, so an attacker can make the page load scripts, styles, or images from an external, attacker-controlled origin and execute arbitrary JavaScript in the site’s context. Details - Affected file : src/runtime/parser/utils/props.ts - Core logic : validateProp() inspects attributes that start with on → blocked href or src → filtered by isAnchorLinkAllowed() Every other attribute and every tag (including <base) is allowed unchanged, so the malicious href on <base is never validated. As soon as <base href="https://vozec.fr" is parsed, any later relative path—/script.js, ../img.png, etc.—is fetched from the attacker’s domain. Proof of Concept Place the following in any Markdown handled by Nuxt MDC: 1. Start the Nuxt app (npm run dev). 2. Visit the page. 3. The browser requests…

Published by the source

20 Jul 2025, 16:36 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:37 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-cj6r-rrr9-fg82

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-cj6r-rrr9-fg82

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# Patch Next advisory brief: CVE-2025-54075

Advisory: Nuxt MDC has an XSS vulnerability in markdown rendering that bypasses HTML filtering
IDs: CVE-2025-54075, GHSA-cj6r-rrr9-fg82
Record: https://patchnext.com/advisories/cve-2025-54075 (revision 2, source checked 26 Oct 2026, 12:37 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @nuxtjs/mdc 0.17.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @nuxtjs/mdc: affected < 0.17.2; fixed in 0.17.2

## Suggested inspection (read-only)
- `npm ls @nuxtjs/mdc --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @nuxtjs/mdc.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-cj6r-rrr9-fg82 (OSV record GHSA-cj6r-rrr9-fg82 lists affected ranges: npm @nuxtjs/mdc >=0 <0.17.2 (fixed))
- Verified: https://github.com/advisories/GHSA-cj6r-rrr9-fg82 (GitHub-reviewed advisory GHSA-cj6r-rrr9-fg82 lists affected ranges: npm @nuxtjs/mdc >=0 <0.17.2)

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