CVE-2026-90505: WARP-Clash-API Race Condition Vulnerability

CVE-2026-90505 Overview

CVE-2026-90505 identifies a race condition [CWE-362] in the doUpdateLicenseKey function of vvbbnn00 WARP-Clash-API. The flaw affects the project up to commit c7bf2360073959861219b422e51ae86411051b46. Attackers can exploit the issue remotely, but exploitation requires high complexity and is reported as difficult. The project does not use versioning, so no fixed release is documented. The vendor was contacted early but did not respond, and the affected product is no longer supported by its maintainer. A public proof-of-concept has been published, increasing the likelihood of opportunistic exploitation attempts.

Critical Impact
Concurrent requests to the license key update path can produce inconsistent state, potentially affecting the confidentiality, integrity, and availability of license data.

Affected Products

vvbbnn00 WARP-Clash-API up to commit c7bf2360073959861219b422e51ae86411051b46
Project uses rolling development without versioned releases
No longer supported by the maintainer

Discovery Timeline

2026-09-13 - CVE-2026-90505 published to NVD
2026-09-14 - Last updated in NVD database

Technical Details for CVE-2026-90505

Vulnerability Analysis

The vulnerability resides in the doUpdateLicenseKey function within WARP-Clash-API. The function updates license key state without adequate synchronization between concurrent execution contexts. An attacker who can issue overlapping requests may trigger a time-of-check to time-of-use (TOCTOU) window, corrupting stored license state or bypassing intended update logic.

Successful exploitation is network-reachable and requires low privileges, but timing sensitivity makes reliable exploitation difficult. Because the project is unmaintained and does not publish releases, defenders cannot rely on a patched build to remediate the flaw. Refer to the VulDB entry for CVE-2026-90505 and the published proof-of-concept for additional technical detail.

Root Cause

The root cause is a missing synchronization primitive around license key state transitions in doUpdateLicenseKey. Two or more concurrent invocations can read, mutate, and write the same underlying resource without mutual exclusion. This class of defect is tracked under CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization.

Attack Vector

An authenticated remote attacker sends parallel HTTP requests targeting the license key update endpoint. When the requests interleave inside the vulnerable function, the resulting race can leave license data in an inconsistent state. Exploitation does not require user interaction, but the attacker must repeatedly race the endpoint to hit the vulnerable window. Reliability depends on server load, request timing, and network jitter.

A verified proof-of-concept is published as a GitHub Gist. Because no code changes have been released by the maintainer, all deployments running the affected commit remain exposed. See the GitHub Gist proof-of-concept for exploitation details.

Detection Methods for CVE-2026-90505

Indicators of Compromise

Bursts of concurrent HTTP requests to the license key update endpoint from a single source IP or client token
Unexpected changes to stored license key records without corresponding administrative action
Application logs showing repeated invocations of doUpdateLicenseKey within very short time windows

Detection Strategies

Instrument the license key update path with request-rate metrics and alert when concurrency exceeds normal baselines
Correlate authentication logs with license state changes to identify update sequences that cannot be explained by legitimate user activity
Deploy web application firewall rules to rate-limit and log parallel requests to the affected endpoint

Monitoring Recommendations

Collect application logs, reverse proxy access logs, and database audit trails into a centralized analytics platform for correlation
Alert on repeated 4xx/5xx response spikes tied to the license key endpoint, which can indicate race exploitation attempts
Track integrity of the license key data store using periodic hash or record-count comparisons

How to Mitigate CVE-2026-90505

Immediate Actions Required

Restrict network exposure of the WARP-Clash-API service to trusted networks or place it behind an authenticated reverse proxy
Rate-limit and serialize requests to the license key update endpoint at the proxy layer
Plan migration off the unmaintained WARP-Clash-API project, since no vendor patch will be issued

Patch Information

No official patch is available. The maintainer did not respond to disclosure, and the project is no longer supported. Because the codebase does not use versioning, downstream operators must apply their own source-level fix by wrapping the doUpdateLicenseKey critical section in a mutex or by enforcing single-flight execution at the request handler level. See the VulDB advisory for additional context.

Workarounds

Add a per-user or per-key lock around license key mutations in a local fork of the source
Front the service with a reverse proxy configured to serialize requests to the vulnerable endpoint
Disable the license key update functionality entirely if it is not required in your deployment

bash

# Example NGINX configuration to serialize requests to the vulnerable endpoint
limit_req_zone $binary_remote_addr zone=license_update:10m rate=1r/s;

location /updateLicenseKey {
    limit_req zone=license_update burst=1 nodelay;
    proxy_pass http://warp_clash_api_backend;
}