auth-fetch-mcp: SSRF and disk exfiltration via unvalidated auth_fetch and download_media URLs

Exploitation

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

CVSS

8.2 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

SSRF + disk-exfil in downloadmedia and authfetch tools — ymw0407/auth-fetch-mcp Severity The downloadmedia and authfetch MCP tools accept arbitrary URLs and reach them as the MCP server process, with downloadmedia additionally persisting the fetched response body to a user-controlled output directory. An MCP client (LLM under prompt injection, malicious peer) can drive the server to fetch loopback / link-local / private-range hosts (cloud-instance metadata, internal services, host-bound services) and exfiltrate the response. Vulnerability chain Site 1: downloadmedia — SSRF + disk-write chain src/tools.ts:200-274 urls and outputdir are user-controlled. The handler iterates each URL (line 236) and calls ctx.request.get(url) (Playwright's APIRequestContext.get) without checking the destination. The response body is written to path.join(outputdir, file-N.ext). Internal-service responses are persisted to disk where they can be exfiltrated via any subsequent tool that reads from the output…

Published by the source

19 May 2026, 15:47 UTC

Last modified by the source

19 May 2026, 16:00 UTC

Source last checked

26 Oct 2026, 12:52 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-hv85-774v-26fg

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-hv85-774v-26fg

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# Patch Next advisory brief: GHSA-hv85-774v-26fg

Advisory: auth-fetch-mcp: SSRF and disk exfiltration via unvalidated auth_fetch and download_media URLs
IDs: GHSA-hv85-774v-26fg
Record: https://patchnext.com/advisories/ghsa-hv85-774v-26fg (revision 2, source checked 26 Oct 2026, 12:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: auth-fetch-mcp 3.0.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm auth-fetch-mcp: affected <= 3.0.0; fixed in 3.0.1

## Suggested inspection (read-only)
- `npm ls auth-fetch-mcp --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 auth-fetch-mcp.
- 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-hv85-774v-26fg (OSV record GHSA-hv85-774v-26fg lists affected ranges: npm auth-fetch-mcp >=0 <3.0.1 (fixed))
- Verified: https://github.com/advisories/GHSA-hv85-774v-26fg (GitHub-reviewed advisory GHSA-hv85-774v-26fg lists affected ranges: npm auth-fetch-mcp >=0 <=3.0.0)

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