CVE-2026-44542

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:** 1. Stable versions (e.g., gtstef/filebrowser:stable) `DELETE /public/api/resources?hash=<hash>&path=../victim` Root cause: middleware.go:111 Issue: path query parameter is joined before SanitizeUserPath() 2. 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](https://github.com/user-attachments/files/26159404/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.

How to fix CVE-2026-44542

To remediate CVE-2026-44542, upgrade the affected package to a fixed version below.

• —upgrade to 0.0.0-20260501183844-112740bdd41d or later

Is CVE-2026-44542 being exploited?

Low — EPSS is 1.0%, meaning exploitation activity has not been observed at scale.