CVE-2026-44542 is a critical-severity (CVSS 9.1) Path Traversal vulnerability in github.com/gtsteffaniak/filebrowser. A fix is available for github.com/gtsteffaniak/filebrowser — see the affected versions and patch details below.
FileBrowser Quantum: Unauthenticated Path Traversal in Public Share Delete Allows Arbitrary File Deletion
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44542.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-44542 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/gtsteffaniak/filebrowserReal-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
Summary
Attacker-controlled path input is joined with a trusted base path prior to sanitization, allowing traversal sequences (e.g., ../) to escape the intended shared directory. As a result, an unauthenticated attacker possessing a valid public share hash with delete permissions enabled can delete arbitrary files outside the shared directory within the share owner’s configured storage scope.
Affected Components
Two distinct vulnerable code paths:
- Stable versions (e.g., gtstef/filebrowser:stable)
DELETE /public/api/resources?hash=<hash>&path=../victimRoot cause: middleware.go:111 Issue: path query parameter is joined before SanitizeUserPath() - Development / HEAD (e.g., commit eabdfd9)
DELETE /public/api/resources/bulk?hash=<hash>Body: [{"path":"../victim"}] Root cause: resource.go:274 Issue: item.Path is joined before SanitizeUserPath()
Steps to reproduce (Stable Version)
1. Create a directory structure:
/folder/shared_subdir/ (shared)
/folder/protected.txt (outside shared directory)
2. Create a public share:
Path: /shared_subdir
AllowDelete=true
3. Send request:
curl -X DELETE "http://localhost/public/api/resources?hash=<HASH>&path=../protected.txt"
#Observe:
#protected.txt is deleted despite being outside the shared directory
Proof of Concept (HEAD / bulk endpoint)
curl -X DELETE "http://localhost/public/api/resources/bulk?hash=<HASH>" \
-H "Content-Type: application/json" \
-d '[{"path":"../protected.txt"}]'
Alternative PoC Scripts:
poc_v3.sh (If the script fails due to environment differences, the manual PoC above reliably reproduces the issue.)
Impact
An unauthenticated attacker with access to a public share link configured with delete permissions enabled can delete attacker-chosen files outside the shared directory, anywhere within the share owner’s storage scope. This results in unauthorized data loss and potential service disruption.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/gtsteffaniak/filebrowser | all versions | 0.0.0-20260501183844-112740bdd41dgo get github.com/gtsteffaniak/filebrowser@v0.0.0-20260501183844-112740bdd41d |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/gtsteffaniak/filebrowser, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/gtsteffaniak/filebrowser to 0.0.0-20260501183844-112740bdd41d or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44542 is resolved across your whole dependency graph.
Workarounds
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-44542 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-44542. 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-2026-44542 in your dependencies?
O3 Security finds CVE-2026-44542 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.