CVE-2026-48777 FileBrowser Quantum: Path Traversal in public share PATCH allows file ops outside shared directory
Attackers with a public share link can move, copy, or rename files outside the shared directory due to path traversal in the PATCH handler.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-48777?
CVE-2026-48777 is a critical path traversal vulnerability in gtsteffaniak filebrowser, published on 16 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
FileBrowser Quantum is a free, self-hosted, web-based file manager. Versions prior to 1.3.2-stable, 1.4.0-beta and 1.4.1-beta are vulnerable to Path Traversal through the publicPatchHandler in backend/http/public.go which joins user-controlled fromPath and toPath body fields with the trusted d.share.Path BEFORE the downstream sanitizer runs. Because filepath.Join collapses .. segments during the join, the sanitizer in resourcePatchHandler never sees the traversal and the move/copy/rename operates on a path outside the shared directory. The same root-cause pattern was patched for the bulk DELETE endpoint as CVE-2026-44542 (GHSA-fwj3-42wh-8673), but the PATCH handler with the identical pattern was not updated. A public share link with AllowModify=true is sufficient to exploit this. Anyone holding such a link can move, copy, or rename arbitrary files within the share owner's source root. This issue has been fixed in versions 1.3.3-stable and 1.4.2-beta.
Weakness: CWE-22
Which versions are affected by CVE-2026-48777?
3 open source packages ship an affected version, including github.com/gtsteffaniak/filebrowser/backend.
| Package | Affected | Fixed in |
|---|---|---|
github.com/gtsteffaniak/filebrowser/backend Go | All versions | 0.0.0-20260518193514-28e9b81e438e |
github.com/gtsteffaniak/filebrowser/backend Go | All versions | 0.0.0-20260518193514-28e9b81e438e |
github.com/gtsteffaniak/filebrowser/backend Go | All versions | 0.0.0-20260518193514-28e9b81e438e |
How do I fix CVE-2026-48777?
Upgrade github.com/gtsteffaniak/filebrowser/backend to 0.0.0-20260518193514-28e9b81e438e or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-48777 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-48777 exists.
Sources
Also known as GHSA-qqqm-5547-774x, GO-2026-5591.