GHSA-6xv5-86q9-7xr8 SecureJoin: on windows, paths outside of the rootfs could be inadvertently produced

Not scored Published 7 Sep 2023

A path traversal vulnerability in the Go filepath-securejoin library allows attackers to access files outside the intended root directory on Windows systems.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Not stated
Victim action needed: Not needed
Fix: Available

What is GHSA-6xv5-86q9-7xr8?

GHSA-6xv5-86q9-7xr8 is a path traversal vulnerability in github.com/cyphar/filepath-securejoin, published on 7 Sep 2023.

Official description

Impact

For Windows users of github.com/cyphar/filepath-securejoin, until v0.2.4 it was possible for certain rootfs and path combinations (in particular, where a malicious Unix-style /-separated unsafe path was used with a Windows-style rootfs path) to result in generated paths that were outside of the provided rootfs.

It is unclear to what extent this has a practical impact on real users, but given the possible severity of the issue we have released an emergency patch release that resolves this issue.

Thanks to @pjbgf for discovering, debugging, and fixing this issue (as well as writing some tests for it).

Patches

c121231e1276e11049547bee5ce68d5a2cfe2d9b is the patch fixing this issue. v0.2.4 contains the fix.

Workarounds

Users could use filepath.FromSlash() on all unsafe paths before passing them to filepath-securejoin.

References

See #9.

Which versions are affected by GHSA-6xv5-86q9-7xr8?

3 open source packages ship an affected version, including github.com/cyphar/filepath-securejoin.

Package	Affected	Fixed in
`github.com/cyphar/filepath-securejoin` Go	All versions	`0.2.4`
`github.com/cyphar/filepath-securejoin` Go	All versions	`0.2.4`
`github.com/cyphar/filepath-securejoin` Go	All versions	`0.2.4`

How do I fix GHSA-6xv5-86q9-7xr8?

Upgrade github.com/cyphar/filepath-securejoin to 0.2.4 or later.

Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.

Is GHSA-6xv5-86q9-7xr8 being exploited?

There is no known exploitation of GHSA-6xv5-86q9-7xr8 in the wild and no public exploit code.

Sources

Also known as GO-2023-2048.