GHSA-FWJ4-72FM-C93G

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

Workarounds

Maintain control of the environment variable settings on your system, in particular the ComSpec environment variable.

References

More information on %ComSpec% can be found online.

More information on Go's PATH-based lookup changes can be found here, here, and here.

A similar issue that was addressed within the Python subprocess module also provides additional discussion.

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 the event that %ComSpec% is not set correctly.

Kodem intelligence

Already deployed Kodem?

The problem has been patched in Mutagen v0.16.6 and v0.17.1. Earlier versions of Mutagen are no longer supported and will not be patched. Versions of Mutagen after v0.18.0 will also have the patch merged.

1. What is GHSA-FWJ4-72FM-C93G? GHSA-FWJ4-72FM-C93G is a low-severity security vulnerability in github.com/mutagen-io/mutagen (go), affecting versions < 0.16.6. It is fixed in 0.16.6, 0.17.1.
2. Which versions of github.com/mutagen-io/mutagen are affected by GHSA-FWJ4-72FM-C93G? github.com/mutagen-io/mutagen (go) versions < 0.16.6 is affected.
3. Is there a fix for GHSA-FWJ4-72FM-C93G? Yes. GHSA-FWJ4-72FM-C93G is fixed in 0.16.6, 0.17.1. Upgrade to this version or later.
4. Is GHSA-FWJ4-72FM-C93G exploitable, and should I be worried? Whether GHSA-FWJ4-72FM-C93G is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether GHSA-FWJ4-72FM-C93G is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix GHSA-FWJ4-72FM-C93G?
   • Upgrade github.com/mutagen-io/mutagen to 0.16.6 or later
   • Upgrade github.com/mutagen-io/mutagen to 0.17.1 or later

Other vulnerabilities in github.com/mutagen-io/mutagen