CVE-2023-36328 Overview
CVE-2023-36328 is a critical Integer Overflow vulnerability discovered in the mp_grow function within libtom libtommath, a widely-used multi-precision integer library. This vulnerability exists in versions prior to commit beba892bc0d4e4ded4d667ab1d2a94f4d75109a9 and allows remote attackers to execute arbitrary code or cause a denial of service (DoS) condition on affected systems.
The libtommath library is commonly used as a foundational component in cryptographic applications and other software requiring large integer arithmetic operations. This makes the vulnerability particularly concerning as it could affect a wide range of downstream applications and systems.
Critical Impact
Remote attackers can execute arbitrary code or trigger denial of service without authentication through network-accessible attack vectors, potentially compromising system integrity and availability.
Affected Products
- libtom libtommath (versions before commit beba892bc0d4e4ded4d667ab1d2a94f4d75109a9)
- Fedora 37
- Fedora 38
- Fedora 39
Discovery Timeline
- 2023-09-01 - CVE-2023-36328 published to NVD
- 2025-06-26 - Last updated in NVD database
Technical Details for CVE-2023-36328
Vulnerability Analysis
The vulnerability resides in the mp_grow function of the libtommath library. This function is responsible for dynamically growing the memory allocation of multi-precision integer structures when additional digit space is required during arithmetic operations.
When processing specially crafted input, the mp_grow function fails to properly validate size calculations, leading to an integer overflow condition. This overflow can result in an undersized memory allocation, which subsequently leads to heap-based buffer overflow conditions when the allocated memory is used.
The vulnerability can be exploited remotely through network-accessible attack vectors without requiring authentication or user interaction. Successful exploitation grants attackers the ability to execute arbitrary code in the context of the affected application or cause the application to crash, resulting in denial of service.
Root Cause
The root cause of CVE-2023-36328 is an Integer Overflow (CWE-190) in the memory size calculation logic within the mp_grow function. When the function calculates the new size for the multi-precision integer array, it performs arithmetic operations that can overflow when handling extremely large values. This results in a much smaller memory allocation than intended, creating conditions where subsequent write operations exceed the allocated buffer boundaries.
Attack Vector
The attack vector for this vulnerability is network-based, allowing remote exploitation without any privileges or user interaction required. An attacker can craft malicious input that triggers the integer overflow condition when processed by applications using the vulnerable libtommath library.
The exploitation mechanism involves:
- Malicious Input Generation: The attacker creates input designed to trigger large size calculations in the mp_grow function
- Integer Overflow Trigger: When the vulnerable function processes this input, the size calculation overflows, wrapping to a small positive value
- Insufficient Memory Allocation: The library allocates a buffer much smaller than required based on the overflowed value
- Memory Corruption: Subsequent operations write beyond the allocated buffer, corrupting adjacent heap memory
- Code Execution or DoS: Depending on the heap layout and attacker control, this can lead to arbitrary code execution or application crash
The vulnerability is particularly dangerous because libtommath is often used in cryptographic applications where untrusted input may be processed during key exchanges, signature verification, or other security-critical operations.
Detection Methods for CVE-2023-36328
Indicators of Compromise
- Unexpected application crashes in processes using libtommath library functions
- Memory corruption errors or heap-related exceptions in application logs
- Abnormal memory allocation patterns or out-of-memory conditions despite sufficient system resources
- Suspicious network traffic patterns delivering malformed cryptographic or mathematical data structures
Detection Strategies
- Monitor for application crashes with stack traces indicating mp_grow or related libtommath functions
- Implement runtime memory corruption detection tools such as AddressSanitizer on development and staging environments
- Deploy file integrity monitoring to detect unauthorized modifications to libtommath shared library files
- Use software composition analysis (SCA) tools to identify vulnerable libtommath versions in deployed applications
Monitoring Recommendations
- Enable detailed crash reporting for applications utilizing libtommath to capture exploitation attempts
- Monitor system logs for unusual heap corruption or segmentation fault patterns in affected applications
- Implement network-level inspection for anomalous data patterns in protocols that utilize multi-precision arithmetic
- Review dependency manifests regularly to identify applications still using vulnerable libtommath versions
How to Mitigate CVE-2023-36328
Immediate Actions Required
- Update libtommath to a version containing commit beba892bc0d4e4ded4d667ab1d2a94f4d75109a9 or later
- Apply Fedora security updates if running Fedora 37, 38, or 39 with the affected package
- Conduct software composition analysis to identify all applications in your environment using the vulnerable library
- Review the libtommath GitHub pull request #546 for technical details on the fix
Patch Information
The vulnerability has been addressed in the libtommath repository. Organizations should update to a version containing the security fix referenced in commit beba892bc0d4e4ded4d667ab1d2a94f4d75109a9. Fedora has released security updates for versions 37, 38, and 39 through the standard package management system. Debian has also issued updates as documented in the Debian LTS Announcement.
For detailed patch information, refer to:
Workarounds
- Implement input validation to restrict the size of mathematical operations processed by libtommath where feasible
- Deploy network segmentation to limit exposure of systems running vulnerable libtommath versions
- Apply sandboxing or containerization for applications using the vulnerable library to limit impact of potential exploitation
- Monitor affected systems closely with enhanced logging until patching can be completed
# Fedora systems: Update libtommath package
sudo dnf update libtommath
# Debian/Ubuntu systems: Check for available security updates
sudo apt update && sudo apt upgrade libtommath1
# Verify installed libtommath version
rpm -q libtommath # For Fedora/RHEL systems
dpkg -l libtommath* # For Debian/Ubuntu systems
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
