CVE-2026-54089
CRITICALCVE-2026-54089 is a critical-severity (CVSS 9.1) Improper Authentication vulnerability in github.com/filebrowser/filebrowser/v2. O3 Security confirms whether CVE-2026-54089 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
File Browser: Authentication Bypass via Proxy Auth Header Forgery
Real-World Exposure
github.com/filebrowser/filebrowser/v2Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/filebrowser/filebrowser/v2 | ≥ 2.0.0-rc.1 | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/filebrowser/filebrowser/v2. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of github.com/filebrowser/filebrowser/v2 has shipped for CVE-2026-54089 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-54089 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-54089. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-54089 in your dependencies?
O3 detects CVE-2026-54089 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.