File Browser: Authentication Bypass via Proxy Auth Header Forgery

Exploitation

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

CVSS

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

EPSS

• CVE-2026-54089: 0.61% estimated exploitation activity in the next 30 days; percentile 49.36 (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 When FileBrowser is configured with proxy authentication (auth.method=proxy), any unauthenticated attacker who can reach the server directly can impersonate any user - including admin - by sending a single forged HTTP header. No credentials are required. Additionally, specifying a non-existent username causes the server to automatically create a new user account, providing an account creation primitive with no authorization. This is an already known issue that has been documented in the documentation for several years, but has not been documented as a vulnerability before. Severity HIGH - CVSS 3.1: 8.1 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N) Affected Component - File: auth/proxy.go, lines 21-28 - CWE: CWE-287 (Improper Authentication), CWE-290 (Authentication Bypass by Spoofing) - Affected versions: All versions supporting auth.method=proxy Prerequisite: Proxy Auth Must Be Enabled This vulnerability is NOT exploitable on default configuration (auth.method=json). It requires the…

Published by the source

10 Jul 2026, 19:27 UTC

Last modified by the source

10 Jul 2026, 19:27 UTC

Source last checked

26 Oct 2026, 15:24 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-xqp3-jq6g-x3qm

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# Patch Next advisory brief: CVE-2026-54089

Advisory: File Browser: Authentication Bypass via Proxy Auth Header Forgery
IDs: CVE-2026-54089, GHSA-xqp3-jq6g-x3qm
Record: https://patchnext.com/advisories/cve-2026-54089 (revision 1, source checked 26 Oct 2026, 15:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/filebrowser/filebrowser/v2: affected >= 2.0.0-rc.1, <= 2.63.18

## Suggested inspection (read-only)
- Go github.com/filebrowser/filebrowser/v2: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## 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-xqp3-jq6g-x3qm (GitHub-reviewed advisory GHSA-xqp3-jq6g-x3qm lists affected ranges: Go github.com/filebrowser/filebrowser/v2 >=2.0.0-rc.1 <=2.63.18)

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