CVE-2024-27280 Overview
A buffer-overread vulnerability was discovered in StringIO 3.0.1, as distributed in Ruby 3.0.x through 3.0.6 and 3.1.x through 3.1.4. The ungetbyte and ungetc methods on a StringIO object can read past the end of a string, and a subsequent call to StringIO.gets may return sensitive memory values. This vulnerability (CWE-120: Buffer Copy without Checking Size of Input) allows attackers to potentially extract sensitive information from process memory without requiring authentication.
Critical Impact
This buffer over-read vulnerability can expose sensitive memory contents including credentials, cryptographic keys, and other application data to remote attackers without authentication.
Affected Products
- StringIO 3.0.1 (as distributed with Ruby)
- Ruby 3.0.x through 3.0.6
- Ruby 3.1.x through 3.1.4
Discovery Timeline
- 2024-03-21 - Ruby Security Advisory published via Ruby News CVE-2024-27280
- 2024-05-14 - CVE CVE-2024-27280 published to NVD
- 2025-11-04 - Last updated in NVD database
Technical Details for CVE-2024-27280
Vulnerability Analysis
The vulnerability resides in the StringIO library's ungetbyte and ungetc methods. These methods are designed to push characters back onto the input stream, effectively "unreading" them. However, due to improper bounds checking, these methods can push data beyond the allocated buffer boundary of the underlying string.
When a subsequent call to StringIO.gets is made, the function may read past the legitimate string boundary and return memory contents that were never part of the original string data. This constitutes a classic buffer over-read condition that can leak sensitive information from the process memory space.
The vulnerability is particularly concerning because StringIO is commonly used for in-memory string manipulation in Ruby applications, including web applications, API servers, and data processing pipelines. An attacker who can influence the input to an application using vulnerable StringIO methods could potentially extract sensitive data from adjacent memory regions.
Root Cause
The root cause is insufficient bounds checking in the ungetbyte and ungetc implementations within the StringIO library. When characters are pushed back onto the stream, the library fails to properly validate that the resulting read position remains within the allocated string buffer. This allows the internal read pointer to reference memory locations outside the intended string boundary, leading to information disclosure when the buffer is subsequently read.
Attack Vector
The attack exploits the network-accessible nature of many Ruby applications. An attacker can craft malicious input that triggers the vulnerable ungetbyte or ungetc methods in a way that causes the internal buffer pointer to exceed legitimate bounds. When the application subsequently calls StringIO.gets, memory contents beyond the original string are returned.
The vulnerability manifests when an application processes user-controlled input through StringIO operations. For technical details on the exploitation mechanics, see the HackerOne Report #1399856 and the Ruby Security Advisory.
Detection Methods for CVE-2024-27280
Indicators of Compromise
- Unexpected or malformed output from Ruby applications containing binary data or memory artifacts
- Application logs showing unusual StringIO operations with large or negative position values
- Memory-related errors or crashes in Ruby applications using StringIO for input processing
Detection Strategies
- Audit Ruby application dependencies using bundle audit or similar tools to identify vulnerable StringIO versions
- Implement runtime monitoring for Ruby applications to detect anomalous StringIO method calls
- Deploy SentinelOne's Singularity platform to detect memory corruption attempts and data exfiltration patterns
- Monitor application outputs for patterns indicative of memory leakage (null bytes, unexpected binary sequences)
Monitoring Recommendations
- Enable verbose logging for Ruby applications processing external input
- Configure SentinelOne to alert on memory access violations in Ruby interpreter processes
- Implement egress monitoring to detect potential data exfiltration following exploitation
- Set up dependency scanning in CI/CD pipelines to prevent deployment of vulnerable versions
How to Mitigate CVE-2024-27280
Immediate Actions Required
- Upgrade StringIO to version 3.0.3 (main fixed version) immediately
- For Ruby 3.0.x environments: Upgrade to StringIO 3.0.1.1
- For Ruby 3.1.x environments: Upgrade to StringIO 3.0.1.2
- Review applications for usage of ungetbyte and ungetc methods and assess exposure
Patch Information
Fixed versions have been released for all affected Ruby versions. The main patched version is StringIO 3.0.3. For compatibility with specific Ruby versions, use StringIO 3.0.1.1 for Ruby 3.0 users and StringIO 3.0.1.2 for Ruby 3.1 users. Additional patch information is available through distribution-specific channels:
Workarounds
- If immediate patching is not possible, audit and restrict use of ungetbyte and ungetc methods
- Implement input validation to limit the size and content of data processed through StringIO
- Consider isolating affected Ruby applications using containerization to limit memory exposure
- Deploy SentinelOne runtime protection to detect and block exploitation attempts
# Update StringIO gem to patched version
gem update stringio
# For bundled applications, update Gemfile
# gem 'stringio', '>= 3.0.3'
bundle update stringio
# Verify installed version
gem list stringio
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
