File Browser: ScopedFs follows a dangling symlink on write, letting a scoped user create files outside their scope

Exploitation

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

CVSS

6.3 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:H/A:N

EPSS

• CVE-2026-55668: 0.38% estimated exploitation activity in the next 30 days; percentile 31.84 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary ScopedFs confines every File Browser user to a scope directory. Its within() guard is meant to reject any operation that follows a symbolic link out of that scope. When the link target does not exist yet, the guard walks up to the nearest existing ancestor and validates that instead. For a dangling symlink (target does not exist), the nearest existing ancestor is the in-scope directory containing the link, so the guard returns "in scope" and the subsequent os.OpenFile(OCREATE) follows the link and creates the file at its out-of-scope target. A post-auth user with Create and Modify permission can write attacker-controlled content to any non-existent path outside their scope that the File Browser process can write to. The precondition is a dangling symlink present inside the user's scope, which is the same out-of-band precondition the rest of ScopedFs is built to defend against. This is a patch-gap variant of the GHSA-239w-m3h6-ch8v symlink confinement issue, not a resubmission…

Published by the source

20 Jul 2026, 21:17 UTC

Last modified by the source

20 Jul 2026, 21:17 UTC

Source last checked

26 Oct 2026, 15:25 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-8wc8-hf36-mjh9

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# Patch Next advisory brief: CVE-2026-55668

Advisory: File Browser: ScopedFs follows a dangling symlink on write, letting a scoped user create files outside their scope
IDs: CVE-2026-55668, GHSA-8wc8-hf36-mjh9
Record: https://patchnext.com/advisories/cve-2026-55668 (revision 1, source checked 26 Oct 2026, 15:25 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/filebrowser/filebrowser/v2 2.63.16. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/filebrowser/filebrowser/v2: affected <= 2.63.15; fixed in 2.63.16

## Suggested inspection (read-only)
- Go github.com/filebrowser/filebrowser/v2: 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/filebrowser/filebrowser/v2.
- 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-8wc8-hf36-mjh9 (GitHub-reviewed advisory GHSA-8wc8-hf36-mjh9 lists affected ranges: Go github.com/filebrowser/filebrowser/v2 >=0 <=2.63.15)

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