HTTPX2 is a next generation HTTP client for Python. Prior to 2.10.0, httpcore2 fails to start TLS in src/httpcore2/httpcore2/_sync/socks_proxy.py and src/httpcore2/httpcore2/_async/socks_proxy.py when the remote origin uses wss through a SOCKS5 proxy because the TLS upgrade condition only recognizes https. HTTPX2 exposes the flaw through Client.websocket() and AsyncClient.websocket() from 2.6.0 through 2.9.1, so the opening handshake, query parameters, Authorization headers, cookies, and subsequent frames can cross the proxy path in plaintext without certificate verification. An attacker controlling or observing that path can read or modify traffic and impersonate the WebSocket server. This issue is fixed in httpcore2 2.10.0 and HTTPX2 2.10.0.

CVE-2026-84381 affects HTTPX2, a Python HTTP client library, versions 2.6.0 through 2.9.1. The vulnerability exists in httpcore2's SOCKS5 proxy implementation, where the TLS upgrade logic only checks for 'https' and fails to handle 'wss' (WebSocket Secure) connections. As a result, WebSocket connections routed through a SOCKS5 proxy are established without TLS encryption and without certificate verification. Sensitive data including the WebSocket handshake, query parameters, Authorization headers, cookies, and WebSocket frames can be transmitted in plaintext. An attacker positioned on the proxy path can perform man-in-the-middle attacks, reading or modifying traffic and impersonating the WebSocket server. The flaw is exposed via the Client.websocket() and AsyncClient.websocket() methods. The issue is fully remediated in httpcore2 2.10.0 and HTTPX2 2.10.0, released by Pydantic.