CVE-2025-54314: Thor Library RCE Vulnerability

CVE-2025-54314 Overview

CVE-2025-54314 is a Command Injection vulnerability affecting Thor, a Ruby toolkit for building command-line interfaces, in versions prior to 1.4.0. The vulnerability exists in a method that can construct an unsafe shell command from library input. However, this CVE is disputed by the supplier, who maintains that "the method that was fixed can only be used with arguments that are controlled by Thor, and there is no way an attacker can take control of those arguments."

Critical Impact
This disputed vulnerability involves unsafe shell command construction that could potentially allow command injection, though the vendor disputes the exploitability due to argument control limitations.

Affected Products

Thor versions prior to 1.4.0
Ruby applications using vulnerable Thor versions for CLI operations
Rails projects with Thor as a dependency

Discovery Timeline

2025-07-20 - CVE CVE-2025-54314 published to NVD
2025-08-10 - Last updated in NVD database

Technical Details for CVE-2025-54314

Vulnerability Analysis

The vulnerability exists in Thor's shell handling functionality, specifically within lib/thor/shell/basic.rb. The vulnerable code used string interpolation to construct shell commands, which is a well-known anti-pattern that can lead to command injection vulnerabilities (CWE-78: Improper Neutralization of Special Elements used in an OS Command).

The attack requires local access with low privileges, though the attack complexity is high. The vulnerability could potentially allow integrity impacts through command manipulation, though confidentiality and availability remain unaffected according to the CVSS assessment.

It's important to note that this CVE is disputed by the Thor maintainers, who assert that the affected method's arguments are internally controlled by Thor and cannot be manipulated by external attackers.

Root Cause

The root cause is the use of unsafe string interpolation when constructing shell commands. The original implementation used Ruby's %() string interpolation syntax to build a command string that was passed to the system() method, which executes the command through the shell.

When using system() with a single interpolated string, the shell interprets special characters, potentially allowing command injection if any portion of the string contains attacker-controlled content.

Attack Vector

The attack vector is local, requiring an attacker to have local access to the system where the vulnerable Thor application is running. The exploitation scenario would involve:

Identifying an application using vulnerable Thor versions
Finding a code path where user-controlled input could reach the affected shell command construction
Crafting malicious input containing shell metacharacters to inject additional commands

The security patch addresses this by switching from shell-interpreted string execution to the safer array-based system() call:

ruby

# Vulnerable code (before patch):
system %(#{merge_tool} "#{temp.path}" "#{destination}")

# Patched code (after fix):
system(merge_tool, temp.path, destination)

Source: GitHub Thor Commit Update

The fix passes arguments as separate parameters to system(), bypassing shell interpretation and preventing command injection.

Detection Methods for CVE-2025-54314

Indicators of Compromise

Unexpected shell command executions originating from Ruby/Thor processes
Unusual process spawning patterns from applications using Thor CLI toolkit
Log entries showing malformed or suspicious command arguments in Thor-based applications

Detection Strategies

Audit Ruby applications for Thor gem versions below 1.4.0 using dependency scanning tools
Monitor for unusual system() calls in Thor-related processes
Implement static code analysis to detect unsafe shell command construction patterns

Monitoring Recommendations

Enable detailed logging for CLI applications built with Thor
Monitor process execution chains for unexpected child processes
Review application logs for shell-related error messages that may indicate exploitation attempts

How to Mitigate CVE-2025-54314

Immediate Actions Required

Upgrade Thor to version 1.4.0 or later where the vulnerability has been addressed
Audit applications using Thor to identify any custom shell command construction patterns
Review the HackerOne Report #3260153 for additional context on the vulnerability

Patch Information

The vulnerability has been addressed in Thor version 1.4.0. The fix modifies the shell command execution to use the safer array-based system() call instead of string interpolation. For detailed patch information, refer to:

Workarounds

Pin Thor dependency to version 1.4.0 or later in your Gemfile
Avoid using Thor's merge tool functionality in untrusted environments until patched
Implement input validation for any user-controllable data that may reach Thor's shell operations

bash

# Update Thor in your Ruby project
bundle update thor

# Or specify minimum version in Gemfile
echo 'gem "thor", ">= 1.4.0"' >> Gemfile
bundle install