CVE-2023-37769: Pixman FPE Vulnerability in stress-test

CVE-2023-37769 Overview

CVE-2023-37769 is a Floating Point Exception (FPE) vulnerability discovered in Pixman, a low-level software library for pixel manipulation. The vulnerability exists in the combine_inner function within the /pixman-combine-float.c component. When exploited, this flaw can cause a denial of service condition by triggering a divide-by-zero or similar floating point exception during pixel combination operations.

Pixman is widely used as a dependency for graphics rendering in many Linux desktop environments and applications, including Cairo graphics library and X.org server, making this vulnerability potentially impactful across numerous systems that rely on graphical rendering capabilities.

Critical Impact

Attackers can cause application crashes and denial of service by providing specially crafted input that triggers a floating point exception in Pixman's pixel combination routines.

Affected Products

• Pixman (all versions prior to fix)
• Applications dependent on Pixman for graphics rendering
• Systems using Cairo graphics library or X.org server with vulnerable Pixman versions

Discovery Timeline

• 2023-07-17 - CVE-2023-37769 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-37769

Vulnerability Analysis

This vulnerability is classified as CWE-369 (Divide By Zero), a type of arithmetic error that occurs when a program attempts to divide a number by zero or performs floating-point operations that result in undefined mathematical conditions. In the context of Pixman, this occurs within the combine_inner function located in pixman-combine-float.c, which handles floating-point pixel combination operations.

The vulnerability can be triggered remotely through a network attack vector, though user interaction is required. An attacker would need to provide malicious input (such as a specially crafted image file) that, when processed by an application using the vulnerable Pixman library, causes the floating-point exception. The result is a complete denial of service as the affected application crashes.

Root Cause

The root cause of CVE-2023-37769 lies in insufficient validation of input values before performing floating-point arithmetic operations in the combine_inner function. When processing certain pixel values or combinations, the code fails to check for conditions that would result in division by zero or other floating-point exceptions. This lack of defensive programming allows malformed or specially crafted input data to reach the vulnerable arithmetic operations, triggering an FPE that crashes the application.

Attack Vector

The attack vector for this vulnerability is network-based with required user interaction. An attacker could exploit this vulnerability through several scenarios:

1. Malicious Image Files: Crafting image files with specific pixel values that, when rendered by applications using Pixman, trigger the FPE condition
2. Web Content: Embedding malicious graphics content on websites that gets processed by browsers or applications using Pixman-based rendering
3. Document Processing: Including malicious images in documents that are rendered by applications dependent on Pixman

The vulnerability does not allow for code execution or information disclosure, but successfully triggering the FPE will cause the affected application to terminate unexpectedly, resulting in denial of service.

For technical details about the vulnerability and its reproduction, refer to the GitLab Issue #76 in the Pixman project repository.

Detection Methods for CVE-2023-37769

Indicators of Compromise

• Application crashes with SIGFPE (Floating Point Exception) signal when processing certain image files
• Core dumps indicating crashes in pixman-combine-float.c or combine_inner function
• Repeated crashes of graphics-dependent applications when handling specific content
• System logs showing FPE-related terminations in applications using Pixman

Detection Strategies

• Monitor application crash logs for SIGFPE signals originating from Pixman library functions
• Implement application-level exception handling to catch and log FPE events before crash
• Use static analysis tools to identify Pixman library versions in deployed applications
• Deploy SentinelOne Singularity platform to detect abnormal application termination patterns

Monitoring Recommendations

• Enable core dump collection for applications using Pixman to aid in forensic analysis
• Monitor system logs for patterns of FPE-related crashes across graphics applications
• Track Pixman library versions across your software inventory for vulnerability management
• Implement alerting on repeated application restarts that may indicate exploitation attempts

How to Mitigate CVE-2023-37769

Immediate Actions Required

• Update Pixman to the latest version that includes the fix for this vulnerability
• Review applications in your environment that depend on Pixman and prioritize updates
• Implement input validation at the application layer for graphics content before passing to Pixman
• Consider temporary deployment of web application firewalls to filter potentially malicious image content

Patch Information

The vulnerability was reported and tracked in the Pixman GitLab Issue #76. Organizations should monitor the official Pixman repository for patches addressing this floating-point exception vulnerability. Contact your Linux distribution vendor for updated Pixman packages that include the security fix.

Since Pixman is commonly distributed through Linux package managers, ensure your systems are configured to receive security updates:

• Debian/Ubuntu: Check for libpixman-1-0 package updates
• RHEL/CentOS/Fedora: Check for pixman package updates
• Arch Linux: Check for pixman package updates

Workarounds

• Implement strict input validation for all image files before processing with Pixman-dependent applications
• Deploy application sandboxing to limit the impact of crashes caused by the vulnerability
• Use process supervision tools to automatically restart affected applications if crashes occur
• Consider disabling or restricting access to graphics processing functionality in sensitive environments until patches are applied

# Check installed Pixman version on Debian/Ubuntu systems
dpkg -l | grep pixman

# Check installed Pixman version on RHEL/CentOS/Fedora systems
rpm -qa | grep pixman

# Update Pixman on Debian/Ubuntu
sudo apt update && sudo apt upgrade libpixman-1-0

# Update Pixman on RHEL/CentOS/Fedora
sudo dnf update pixman