CVE-2026-42371 Overview
A numeric truncation vulnerability exists in uriparser before version 1.0.1 that affects text range comparison operations. This vulnerability is classified as CWE-197 (Numeric Truncation Error) and occurs when an application processes URIs with extremely large lengths, specifically in the gigabyte range. The improper handling of numeric values during text range comparisons can lead to unexpected behavior and potential denial of service conditions.
Critical Impact
Applications processing extremely large URIs through uriparser may experience denial of service due to numeric truncation in text range comparison logic.
Affected Products
- uriparser versions prior to 1.0.1
Discovery Timeline
- April 27, 2026 - CVE-2026-42371 published to NVD
- April 27, 2026 - Last updated in NVD database
Technical Details for CVE-2026-42371
Vulnerability Analysis
The vulnerability stems from improper handling of numeric values when comparing text ranges within URI processing operations. When applications accept URIs with lengths in the gigabyte range, the internal comparison mechanisms experience numeric truncation due to data type limitations. This truncation can cause text range comparisons to return incorrect results, potentially leading to application crashes or unpredictable behavior.
The local attack vector requires an attacker to have access to the system where the vulnerable application is running. While no user interaction is required, the attack complexity is considered high due to the specific conditions needed to trigger the vulnerability—namely, the application must be configured to accept and process extremely large URIs.
Root Cause
The root cause is a Numeric Truncation Error (CWE-197) in the text range comparison functionality. When the uriparser library processes URIs with lengths that exceed the capacity of the numeric data types used for range comparisons, the values are truncated. This truncation occurs silently, causing the comparison logic to operate on incorrect values and potentially returning erroneous results.
Attack Vector
The attack requires local access to a system running an application that uses the vulnerable uriparser library. An attacker must craft a malicious URI with an extremely large length (in the gigabyte range) and submit it to the vulnerable application. When the application processes this URI, the numeric truncation in text range comparison can cause high availability impact through denial of service conditions.
The vulnerability mechanism involves the text range comparison functions within uriparser that are susceptible to numeric overflow when handling URI lengths exceeding normal operational parameters. Technical details regarding the specific fix can be found in the GitHub Pull Request #298.
Detection Methods for CVE-2026-42371
Indicators of Compromise
- Applications processing unusually large URI inputs (gigabyte-scale)
- Unexpected application crashes during URI parsing operations
- Memory allocation anomalies related to URI handling functions
Detection Strategies
- Monitor application logs for errors related to URI parsing failures
- Implement input validation to detect and reject abnormally large URI submissions
- Use application performance monitoring to identify unusual resource consumption during URI processing
Monitoring Recommendations
- Configure alerts for application crashes in services that utilize uriparser
- Monitor system resource utilization for abnormal memory consumption patterns
- Review and audit applications that accept user-supplied URIs for proper input length validation
How to Mitigate CVE-2026-42371
Immediate Actions Required
- Upgrade uriparser to version 1.0.1 or later
- Implement input validation to restrict maximum URI length in applications using uriparser
- Review application configurations to ensure unnecessary acceptance of extremely large URIs is disabled
Patch Information
The vulnerability has been addressed in uriparser version 1.0.1. The fix corrects the numeric truncation issue in text range comparison operations. For detailed information about the patch, refer to the GitHub Pull Request #298. Additional information is available at the UriParser Project Site and the Openwall OSS-Security Discussion.
Workarounds
- Implement application-level input validation to enforce reasonable URI length limits
- Configure web servers and application firewalls to reject requests with extremely large URIs
- Monitor and limit resource allocation for URI parsing operations
# Example: Limit URI length at application level before passing to uriparser
# Set maximum URI length to a reasonable value (e.g., 8KB)
MAX_URI_LENGTH=8192
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
