CVE-2022-41409: Pcre2 Integer Overflow DOS Vulnerability

CVE-2022-41409 Overview

CVE-2022-41409 is an integer overflow vulnerability affecting the pcre2test utility in PCRE2 (Perl Compatible Regular Expressions 2) versions prior to 10.41. This vulnerability allows attackers to cause a denial of service or potentially trigger other unspecified impacts by providing negative input values in test subject lines, leading to infinite looping conditions.

Critical Impact

This integer overflow vulnerability can result in denial of service through infinite loops when processing maliciously crafted negative repeat values, potentially affecting applications and systems that rely on PCRE2 for regular expression processing.

Affected Products

• PCRE2 versions prior to 10.41
• pcre2test testing utility component
• Systems and applications utilizing vulnerable PCRE2 library versions

Discovery Timeline

• 2023-07-18 - CVE-2022-41409 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-41409

Vulnerability Analysis

This vulnerability stems from an integer overflow condition (CWE-190) within the pcre2test utility. When the utility processes subject lines containing repeat values, it fails to properly validate and diagnose negative input values. This improper input validation leads to an integer overflow condition that causes the application to enter an infinite loop, consuming CPU resources indefinitely.

The pcre2test utility is a command-line program used for testing PCRE2 regular expression patterns. While primarily a testing tool, the underlying integer handling issues it exhibits could have broader implications for applications integrating PCRE2 functionality without proper input sanitization.

Root Cause

The root cause of CVE-2022-41409 is the absence of proper validation for negative repeat values in pcre2test subject line processing. When a negative value is provided where a positive repeat count is expected, the integer overflow occurs, and the application fails to detect or handle this invalid condition appropriately. This results in undefined behavior manifesting as infinite loop execution.

Attack Vector

The attack vector is network-based, requiring no privileges or user interaction. An attacker can exploit this vulnerability by:

1. Providing crafted input containing negative repeat values to the pcre2test utility
2. Triggering the integer overflow condition through malformed test data
3. Causing the application to enter an infinite loop, resulting in denial of service

The vulnerability can be exploited remotely if the pcre2test utility or applications using similar PCRE2 functionality process untrusted input from network sources.

// Security patch excerpt from ChangeLog
 produced errors when building for Windows with #define PCRE2_CALL_CONVENTION
 __stdcall.
 
+20. A negative repeat value in a pcre2test subject line was not being 
+diagnosed, leading to infinite looping.
+
 
Version 10.40 15-April-2022
---------------------------

Source: GitHub Commit 94e1c001761373b7d9450768aa15d04c25547a35

Detection Methods for CVE-2022-41409

Indicators of Compromise

• Unusual CPU utilization spikes associated with pcre2test or PCRE2-dependent processes
• Application hang conditions or unresponsive behavior during regular expression processing
• System resource exhaustion from processes stuck in infinite loops
• Log entries indicating abnormal or malformed input being processed by PCRE2 components

Detection Strategies

• Monitor for processes exhibiting high CPU utilization with no corresponding I/O activity
• Implement application-level logging to track input validation failures in PCRE2 processing routines
• Deploy behavioral analysis to detect anomalous looping patterns in regex processing applications
• Use static analysis tools to identify applications using vulnerable PCRE2 library versions

Monitoring Recommendations

• Configure resource monitoring alerts for pcre2test and related processes
• Implement process watchdogs to detect and terminate hung processes
• Review application logs for evidence of integer overflow or boundary condition errors
• Maintain an inventory of systems running vulnerable PCRE2 versions for targeted monitoring

How to Mitigate CVE-2022-41409

Immediate Actions Required

• Upgrade PCRE2 to version 10.41 or later immediately
• Audit systems to identify all instances of vulnerable PCRE2 installations
• Implement input validation to filter negative values before passing data to PCRE2 functions
• Apply process resource limits to prevent denial of service from infinite loops

Patch Information

The PCRE2 project has addressed this vulnerability in version 10.41. The security fix adds proper diagnosis and handling of negative repeat values in pcre2test subject lines, preventing the infinite loop condition. Organizations should apply this update by obtaining the patched version from the official PCRE2 repository.

The specific fix is available in GitHub commit 94e1c001761373b7d9450768aa15d04c25547a35. Additional technical discussion can be found in the GitHub issue #141.

Workarounds

• Implement input sanitization to reject negative repeat values before PCRE2 processing
• Deploy application-level timeouts for regular expression operations to prevent infinite loops
• Restrict access to pcre2test utility to trusted users and environments only
• Use process isolation and resource limits (cgroups, ulimit) to contain potential denial of service impacts

# Configuration example - Process resource limits
# Add to /etc/security/limits.conf or use ulimit
# Limit CPU time to prevent infinite loop resource exhaustion
ulimit -t 60  # Limit CPU time to 60 seconds

# Alternative: Use timeout command for pcre2test operations
timeout 30s pcre2test -options input_file

# Implement cgroup CPU limits for PCRE2 processes
cgcreate -g cpu:/pcre2_limited
cgset -r cpu.cfs_quota_us=50000 pcre2_limited
cgexec -g cpu:pcre2_limited /usr/bin/pcre2test