CVE-2022-28739: Ruby-lang Ruby Buffer Overflow Vulnerability

CVE-2022-28739 Overview

CVE-2022-28739 is a buffer over-read vulnerability affecting multiple versions of the Ruby programming language. The flaw exists in Ruby's String-to-Float conversion functionality, specifically impacting the Kernel#Float and String#to_f methods. When processing specially crafted input strings, Ruby fails to properly validate buffer boundaries during the conversion process, allowing attackers to read memory beyond the intended buffer limits.

This out-of-bounds read vulnerability (CWE-125) can be exploited remotely without authentication, potentially exposing sensitive information stored in adjacent memory regions. The vulnerability affects Ruby versions before 2.6.10, 2.7.x before 2.7.6, 3.x before 3.0.4, and 3.1.x before 3.1.2.

Critical Impact

Attackers can exploit this buffer over-read to extract sensitive data from process memory, potentially including cryptographic keys, authentication tokens, or other confidential information processed by Ruby applications.

Affected Products

• Ruby-lang Ruby (versions before 2.6.10, 2.7.x before 2.7.6, 3.x before 3.0.4, 3.1.x before 3.1.2)
• Debian Linux 9.0, 10.0, 11.0
• Apple macOS (multiple versions)

Discovery Timeline

• April 12, 2022 - Ruby-lang releases security advisory
• May 9, 2022 - CVE-2022-28739 published to NVD
• November 4, 2025 - Last updated in NVD database

Technical Details for CVE-2022-28739

Vulnerability Analysis

This vulnerability stems from improper bounds checking in Ruby's floating-point number parsing routines. When a Ruby application converts a string to a floating-point number using either Kernel#Float() or the String#to_f method, the underlying C implementation fails to properly validate the length of the input string against the allocated buffer size.

The buffer over-read condition occurs during the parsing phase where Ruby iterates through string characters to construct the floating-point representation. Without adequate boundary validation, the parser can continue reading past the end of the allocated string buffer, accessing adjacent memory regions.

This type of vulnerability is particularly concerning in web applications and services that process user-supplied data, as attackers can craft malicious input strings designed to trigger the over-read and potentially leak sensitive information from the application's memory space.

Root Cause

The root cause is inadequate bounds checking in Ruby's internal String-to-Float conversion implementation. The parsing routine does not properly verify that memory access operations remain within the bounds of the input string buffer, allowing reads beyond the intended data boundary. This represents a classic CWE-125 (Out-of-bounds Read) vulnerability pattern in native code handling.

Attack Vector

The attack vector is network-based, requiring no privileges or user interaction. An attacker can exploit this vulnerability by sending specially crafted string values to any Ruby application endpoint that performs String-to-Float conversion on user-controlled input.

Exploitation scenarios include:

• Web applications processing numeric form inputs
• API endpoints parsing JSON/XML with numeric string values
• Ruby-based services processing configuration or data files

The vulnerability can be triggered by passing malicious strings to functions like Float("malicious_string") or "malicious_string".to_f where the string is designed to cause the parser to read beyond buffer boundaries.

Detection Methods for CVE-2022-28739

Indicators of Compromise

• Unusual memory access patterns in Ruby processes during string conversion operations
• Unexpected application crashes or errors related to floating-point parsing
• Anomalous network traffic containing malformed numeric strings targeting Ruby applications
• Memory disclosure in application responses or logs

Detection Strategies

• Monitor Ruby application logs for errors related to String-to-Float conversion or memory access violations
• Implement application-layer firewalls to detect and block malformed numeric string payloads
• Deploy memory safety monitoring tools to detect out-of-bounds read operations in Ruby processes
• Conduct regular vulnerability scanning to identify unpatched Ruby installations

Monitoring Recommendations

• Enable verbose logging for Ruby applications to capture conversion errors and potential exploitation attempts
• Monitor system memory usage patterns for anomalies that may indicate memory disclosure attacks
• Implement intrusion detection rules for network traffic containing suspicious numeric string patterns
• Review application inputs that undergo String-to-Float conversion for potential abuse

How to Mitigate CVE-2022-28739

Immediate Actions Required

• Upgrade Ruby to patched versions: 2.6.10+, 2.7.6+, 3.0.4+, or 3.1.2+
• Inventory all systems running vulnerable Ruby versions across your infrastructure
• Prioritize patching internet-facing Ruby applications that process user input
• Apply vendor patches for affected operating systems including Debian Linux and Apple macOS

Patch Information

Ruby-lang has released patched versions addressing this vulnerability. Organizations should upgrade to Ruby 2.6.10, 2.7.6, 3.0.4, or 3.1.2 or later depending on their current version branch. The official security advisory is available at the Ruby Language News page.

Additional patches are available from operating system vendors:

• Debian CVE Tracker provides updates for Debian Linux
• Apple has released fixes documented in HT213488, HT213493, and HT213494
• Gentoo GLSA 202401-27 addresses this vulnerability for Gentoo users
• NetApp Security Advisory NTAP-20220624-0002 provides guidance for NetApp products

Workarounds

• Implement strict input validation on all strings before conversion to floating-point numbers
• Limit the length and character set of numeric string inputs at the application layer
• Use web application firewalls to filter potentially malicious numeric string payloads
• Consider containerization or sandboxing for Ruby applications to limit memory disclosure impact

# Check Ruby version and upgrade
ruby --version
# Upgrade via package manager (example for Debian/Ubuntu)
sudo apt update && sudo apt upgrade ruby
# Or use rbenv/rvm to install patched version
rbenv install 3.1.2
rbenv global 3.1.2