CVE-2024-27282: Ruby Regex Information Disclosure Flaw

CVE-2024-27282 Overview

An out-of-bounds read vulnerability was discovered in Ruby's regex compiler that allows attackers to extract arbitrary heap data. When attacker-supplied data is provided to the Ruby regex compiler, it becomes possible to read memory contents relative to the start of the text buffer, including sensitive information such as pointers and strings stored in heap memory.

Critical Impact

This vulnerability enables attackers to extract sensitive data from heap memory through malicious regex patterns, potentially exposing authentication tokens, cryptographic keys, and other confidential information processed by Ruby applications.

Affected Products

• Ruby 3.0.x through 3.0.6
• Ruby 3.1.x through 3.1.4
• Ruby 3.2.x through 3.2.3
• Ruby 3.3.0

Discovery Timeline

• 2024-04-23 - Ruby project releases security advisory
• 2024-05-14 - CVE-2024-27282 published to NVD
• 2025-11-04 - Last updated in NVD database

Technical Details for CVE-2024-27282

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read) and affects Ruby's regular expression compilation engine. The flaw exists in how the regex compiler handles attacker-controlled input data, allowing memory reads beyond the intended buffer boundaries.

When a Ruby application processes user-supplied data through the regex compiler, the vulnerability permits extraction of heap memory contents relative to the text being processed. This means an attacker can craft specific input patterns that cause the regex engine to read and potentially return memory contents that should not be accessible, including memory addresses, internal pointers, and sensitive string data stored elsewhere in the process heap.

The local attack vector requires user interaction, meaning an attacker would need to convince a user to process malicious input or exploit an application that processes untrusted regex patterns. Despite requiring local access and user interaction, the vulnerability presents significant confidentiality risks due to the potential exposure of sensitive heap data.

Root Cause

The root cause lies in improper bounds checking within Ruby's regex compilation routine. The regex compiler fails to properly validate memory access boundaries when processing certain input patterns, allowing reads to occur outside the allocated text buffer. This boundary validation failure enables an attacker to leverage the regex engine as an oracle for reading arbitrary heap memory locations relative to the input text's position in memory.

Attack Vector

The attack requires local access with user interaction. An attacker must craft malicious input that gets processed by Ruby's regex compiler. This could occur in scenarios where:

• A web application accepts user-provided regex patterns for search functionality
• A command-line tool processes untrusted input through regex matching
• A service deserializes or processes data containing regex patterns from untrusted sources

The attacker provides specially crafted data to the regex compiler, which then reads heap memory beyond intended boundaries. The extracted data may include sensitive information such as session tokens, passwords, cryptographic material, or memory layout information that could facilitate further exploitation.

Detection Methods for CVE-2024-27282

Indicators of Compromise

• Unusual regex patterns in application logs that contain non-standard or escape sequences
• Ruby applications exhibiting unexpected memory access patterns or crashes
• Error messages indicating regex compilation failures with suspicious input
• Memory disclosure in application responses that includes unexpected binary data

Detection Strategies

• Monitor Ruby applications for regex operations involving user-supplied input patterns
• Implement logging for regex compilation operations to identify suspicious patterns
• Deploy application-level monitoring to detect unusual memory access patterns in Ruby processes
• Use static analysis tools to identify code paths where untrusted data reaches regex compilation functions

Monitoring Recommendations

• Enable verbose logging for Ruby applications processing user input through regex engines
• Monitor system logs for Ruby process crashes or abnormal terminations related to regex operations
• Implement intrusion detection rules for known exploitation patterns targeting this vulnerability
• Review application traffic for unusually long or malformed regex patterns in request parameters

How to Mitigate CVE-2024-27282

Immediate Actions Required

• Upgrade Ruby to patched versions: 3.0.7, 3.1.5, 3.2.4, or 3.3.1 immediately
• Audit applications for code paths where untrusted input is passed to regex compilation functions
• Implement input validation to reject suspicious regex patterns before compilation
• Consider sandboxing Ruby applications that must process untrusted regex input

Patch Information

Ruby has released fixed versions addressing this vulnerability. The patched versions are:

• Ruby 3.0.7 for the 3.0.x branch
• Ruby 3.1.5 for the 3.1.x branch
• Ruby 3.2.4 for the 3.2.x branch
• Ruby 3.3.1 for the 3.3.x branch

Administrators should update to the appropriate patched version for their Ruby branch. For detailed patch information, refer to the Ruby Security Advisory and the HackerOne Report #2122624.

Distribution-specific updates are available through Debian LTS and Fedora package repositories.

Workarounds

• Sanitize all user input before passing to Ruby regex functions by removing or escaping special regex characters
• Implement allowlisting for regex patterns if dynamic pattern generation is required
• Use alternative string matching methods that do not involve regex compilation for untrusted input
• Deploy web application firewalls configured to detect and block suspicious regex patterns

# Verify Ruby version and upgrade if vulnerable
ruby --version
# If vulnerable, upgrade using your package manager
# For rbenv users:
rbenv install 3.3.1
rbenv global 3.3.1
# For system Ruby on Debian/Ubuntu:
sudo apt update && sudo apt upgrade ruby
# Verify the upgrade
ruby --version