# 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.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Jun 2026
- **Updated:** 17 Jun 2026
- **Also known as:** GHSA-qqqm-5547-774x, GO-2026-5591

## 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 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-48777?

3 open source packages ship an affected version, including github.com/gtsteffaniak/filebrowser/backend.


| Package | Ecosystem | 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.

## Is CVE-2026-48777 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-48777 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-48777 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-48777 exists.

Affected packages and fixed versions:
- github.com/gtsteffaniak/filebrowser/backend (Go): affected all versions; fixed in 0.0.0-20260518193514-28e9b81e438e
- github.com/gtsteffaniak/filebrowser/backend (Go): affected all versions; fixed in 0.0.0-20260518193514-28e9b81e438e
- github.com/gtsteffaniak/filebrowser/backend (Go): affected all versions; fixed in 0.0.0-20260518193514-28e9b81e438e

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-48777/ (Markdown: https://insights.sbomify.com/CVE-2026-48777/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-48777
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-48777
- OSV: https://osv.dev/vulnerability/CVE-2026-48777

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-48777/
Summaries are generated and may contain mistakes; the official description above is the record.