claude-faf-mcp has an arbitrary local file read/write via unconfined path argument in FAF tools

Exploitation

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

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary claude-faf-mcp MCP tools accept a caller-controlled path argument and resolve it (~ expansion + path.resolve()) straight into a filesystem read/write without confining it to a trusted project directory. An absolute path or ../ traversal is resolved and used as-is, so the server process can be made to read — and, via the file tools, write — files outside the intended .faf project context. The only remaining limit is OS file permissions. Affected tools The shared getProjectPath() chokepoint (feeding the .faf tools) and the general-purpose fafread / fafwrite file tools resolved a caller path straight into a read/write with no confinement (denylist-only); an absolute path still reached home-directory secrets, and fafwrite could write outside the project. Impact An MCP client — or an LLM prompt-injected via attacker-controlled content (a web page, README, ticket, or .faf) into issuing a tool call — can read any file the server process can read: SSH keys (~/.ssh/idrsa), cloud…

Published by the source

19 Aug 2026, 19:15 UTC

Last modified by the source

19 Aug 2026, 19:15 UTC

Source last checked

26 Oct 2026, 13:01 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-rr55-jp92-8wp2

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# Patch Next advisory brief: GHSA-rr55-jp92-8wp2

Advisory: claude-faf-mcp has an arbitrary local file read/write via unconfined `path` argument in FAF tools
IDs: GHSA-rr55-jp92-8wp2
Record: https://patchnext.com/advisories/ghsa-rr55-jp92-8wp2 (revision 1, source checked 26 Oct 2026, 13:01 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: claude-faf-mcp 5.7.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm claude-faf-mcp: affected <= 5.7.1; fixed in 5.7.2

## Suggested inspection (read-only)
- `npm ls claude-faf-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 claude-faf-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://github.com/advisories/GHSA-rr55-jp92-8wp2 (GitHub-reviewed advisory GHSA-rr55-jp92-8wp2 lists affected ranges: npm claude-faf-mcp >=0 <=5.7.1)

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