CVE-2026-44927: Uriparser Buffer Overflow Vulnerability

CVE-2026-44927 Overview

CVE-2026-44927 affects uriparser, a widely used C library for parsing Uniform Resource Identifiers (URIs) per RFC 3986. Versions before 1.0.2 truncate pointer differences when assigning them to int variables in multiple locations. The defect maps to [CWE-197: Numeric Truncation Error]. An attacker who supplies a crafted URI to an application linked against vulnerable uriparser can trigger incorrect length calculations, leading to limited integrity impact over the network without authentication or user interaction.

Critical Impact
Network-reachable applications parsing untrusted URIs with uriparser versions before 1.0.2 may compute incorrect offsets, corrupting downstream parsing logic and producing inconsistent integrity outcomes.

Affected Products

uriparser versions prior to 1.0.2
Applications statically linking the vulnerable uriparser library
Distributions and packages redistributing affected uriparser builds

Discovery Timeline

2026-05-08 - CVE-2026-44927 published to the National Vulnerability Database (NVD)
2026-05-12 - Last updated in NVD database

Technical Details for CVE-2026-44927

Vulnerability Analysis

The defect is a numeric truncation error. uriparser computes pointer differences using ptrdiff_t, which is typically 64-bit on modern platforms. Several code paths assign these results to variables of type int, which is typically 32-bit. When the pointer difference exceeds INT_MAX, the high-order bits are silently discarded.

The truncated value then flows into length calculations and offset arithmetic inside the URI parser. The parser proceeds with values that no longer correspond to the original input size. This produces inconsistent parse results and limited integrity impact in calling applications.

Exploitation requires the application to feed an attacker-controlled URI into uriparser. The attack vector is network-accessible because URIs commonly arrive from HTTP requests, configuration retrieved from remote services, and user-supplied input in web-facing components.

Root Cause

The root cause is improper type selection. uriparser casts or implicitly converts ptrdiff_t results to int in several functions that handle URI component boundaries. The fix in version 1.0.2 widens the storage types and adds explicit range checks, removing the silent truncation.

Attack Vector

An attacker submits a URI long enough or structured to produce a pointer difference outside the representable range of int. The parser miscomputes a boundary and returns inconsistent state to the caller. The integrity impact is limited; confidentiality and availability are not directly affected per the assigned CVSS metrics.

No verified public proof-of-concept code is available. Refer to the uriparser pull request #304 for the source-level changes that remediate the issue.

Detection Methods for CVE-2026-44927

Indicators of Compromise

Application logs showing inconsistent URI parsing results or unexpected component lengths returned from uriparser APIs
Crash dumps or assertion failures originating from functions within the uriparser library
Unusually large URI payloads submitted to network-facing endpoints that link against uriparser

Detection Strategies

Inventory all binaries and packages that statically or dynamically link uriparser and compare versions against 1.0.2
Use Software Composition Analysis (SCA) tooling to flag uriparser versions earlier than 1.0.2 in source repositories and container images
Apply web application firewall (WAF) rules to identify abnormally long URIs targeting services known to use uriparser

Monitoring Recommendations

Monitor process telemetry for crashes or abnormal exits in services that parse external URIs
Track outbound and inbound HTTP traffic for oversized URI fields that exceed reasonable application limits
Centralize application error logs to detect repeated parser failures indicative of probing

How to Mitigate CVE-2026-44927

Immediate Actions Required

Upgrade uriparser to version 1.0.2 or later across all systems
Rebuild and redeploy applications that statically link uriparser after upgrading the dependency
Audit third-party software and container images for embedded copies of vulnerable uriparser versions

Patch Information

The upstream fix is delivered in uriparser1.0.2. The corresponding source changes are described in the uriparser GitHub Pull Request #304, which widens the affected variables and removes the unsafe narrowing conversions.

Workarounds

Enforce strict input length limits on URIs at network ingress before they reach uriparser
Reject requests whose URI length exceeds documented application maximums at the reverse proxy or WAF tier
Where upgrade is not yet possible, isolate services that parse untrusted URIs behind additional validation layers

bash

# Verify installed uriparser version on Linux distributions
dpkg -l | grep -i uriparser    # Debian/Ubuntu
rpm -qa | grep -i uriparser    # RHEL/Fedora/SUSE

# Example WAF rule snippet to cap URI length (ModSecurity)
SecRule REQUEST_URI "@gt 2048" \
    "id:1009001,phase:1,deny,status:414,msg:'URI length exceeds policy limit'"