Under-validated ComSpec and cmd.exe resolution in Mutagen projects

Exploitation

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

CVSS

not scored

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Impact Mutagen projects offer shell-based execution functionality. On Windows, the shell is resolved using the standard %ComSpec% mechanism, with a fallback to a %PATH%-based search for cmd.exe. While this is the standard practice on Windows systems, it presents somewhat risky behavior. Firstly, %ComSpec% could, in theory, be set maliciously. Unfortunately, there's not much that can be done to prevent this attack surface, because %ComSpec% is the official mechanism for shell specification on Windows. We can, however, validate that it points to an absolute path, which one would expect for a properly set value. Secondly, a fallback to a relative cmd.exe path, resolved via %PATH%, could be risky. The risk is largely mitigated by changes in Go 1.19 and later, but prior to that a malicious cmd.exe could been resolved in the current working directory. To mitigate this issue, Mutagen now uses the %SystemRoot% environment variable (also validated to be an absolute path) to resolve cmd.exe in…

Published by the source

5 May 2023, 02:18 UTC

Last modified by the source

5 May 2023, 02:18 UTC

Source last checked

26 Oct 2026, 14:58 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-fwj4-72fm-c93g

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: GHSA-fwj4-72fm-c93g

Advisory: Under-validated ComSpec and cmd.exe resolution in Mutagen projects
IDs: GHSA-fwj4-72fm-c93g
Record: https://patchnext.com/advisories/ghsa-fwj4-72fm-c93g (revision 1, source checked 26 Oct 2026, 14:58 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/mutagen-io/mutagen 0.17.1, 0.16.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/mutagen-io/mutagen: affected < 0.16.6; >= 0.17.0, < 0.17.1; fixed in 0.16.6, 0.17.1

## Suggested inspection (read-only)
- Go github.com/mutagen-io/mutagen: check the installed version with your package manager.

## 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 github.com/mutagen-io/mutagen.
- 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-fwj4-72fm-c93g (GitHub-reviewed advisory GHSA-fwj4-72fm-c93g lists affected ranges: Go github.com/mutagen-io/mutagen >=0 =0.17.0 <0.17.1)

Commands are suggestions: review each one before running it.