CVE-2026-38637: relibc pthread_rwlockattr_setpshared() Remote Denial of Service Vulnerability

Technical summary

CVE-2026-38637 is a denial-of-service vulnerability in relibc commit 61f42d affecting the pthread_rwlockattr_setpshared() function, a POSIX thread synchronization utility. The vulnerability stems from insufficient input validation (CWE-400: Uncontrolled Resource Consumption), permitting attackers to supply crafted parameters that exhaust system resources or trigger unhandled exceptions, resulting in process termination or service unavailability. The network-accessible attack surface, combined with the absence of privilege or interaction requirements, yields a CVSS v3.1 score of 7.5 (HIGH).

Business impact

Services relying on relibc for thread synchronization are vulnerable to disruption. An attacker can remotely invoke the affected function through affected applications, causing application crashes, service restarts, or availability outages. For systems running relibc-dependent workloads—particularly multi-threaded applications managing concurrency—this translates to direct business continuity risk. The impact scales with the number of exposed relibc-dependent services and their criticality to operations.

Affected systems

relibc commit 61f42d and related versions containing the vulnerable pthread_rwlockattr_setpshared() function are affected. relibc is a portable C library implementation often used in embedded systems, educational environments, and specialized runtime contexts. You should identify which of your applications or services explicitly depend on relibc and confirm their commit versions. No specific product CVE bindings were disclosed in available data; verification against relibc's official repository and your own software bill of materials (SBOM) is required.

Exploitability

Exploitability is high. The vulnerability requires only network access and crafted input—no authentication, privilege escalation, or user interaction is needed. An attacker can directly call or trigger the vulnerable function if the application exposes it through network interfaces, APIs, or inter-process communication mechanisms. The attack is repeatable and does not depend on race conditions or probabilistic timing.

Remediation

Update relibc to a patched commit that addresses the input validation flaw in pthread_rwlockattr_setpshared(). Consult the relibc project repository for available patches post-commit 61f42d. If immediate patching is not feasible, implement network-level controls to restrict access to applications that depend on the vulnerable library, and monitor for abnormal service terminations or crashes that may indicate exploitation attempts.

Patch guidance

Check the relibc project's official repository and release notes for patches addressing CVE-2026-38637. Patches should be applied to all systems running the affected commit. Verify the patched version by confirming the commit hash or release version matches the fix. Test patches in a non-production environment before deployment to ensure compatibility with dependent applications. Consider automating updates for relibc dependencies in your build and deployment pipelines.

Detection guidance

Monitor application logs and system metrics for unexpected crashes, service restarts, or DoS-like behaviors in relibc-dependent processes. Network intrusion detection systems should flag requests that appear to target pthread synchronization functions with unusual parameters. Implement application-level logging around pthread_rwlockattr_setpshared() calls to capture input and detect anomalies. Correlate service availability incidents with resource exhaustion patterns or unhandled exception signatures.

Why prioritize this

Assign this vulnerability HIGH priority due to its remote exploitability, lack of authentication barriers, and direct impact on service availability. However, actual risk depends on whether your environment uses relibc and how exposed those services are to untrusted networks. Organizations not using relibc face minimal risk; those deploying relibc-dependent applications in internet-facing or high-criticality roles should prioritize patching within 2–4 weeks.

Risk score, explained

The CVSS v3.1 score of 7.5 reflects a remotely exploitable, unauthenticated attack requiring only low complexity input, targeting availability (not confidentiality or integrity). The score does not account for organizational context—actual risk is lower for organizations that do not use relibc, and higher for those running relibc in critical, exposed services. Validate your exposure before adjusting internal risk ratings.

Frequently asked questions