goproxy through 15.3 Authentication Bypass via CONNECT

Advisories

goproxy through 15.3 Authentication Bypass via CONNECT

severity: medium
date: 9/14/2026
Affecting: goproxy <= 15.3
CVE: CVE-2026-91143
CWE: CWE-288 Authentication Bypass Using an Alternate Path or Channel
CVSS: 6.9
CVSS V4 Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
References: Researcher write-up
utils/structs.go at v15.3
services/http.go at v15.3
https://github.com/snail007/goproxy
Credit: George Chen
Description: goproxy through 15.3 fails to apply HTTP proxy basic authentication to CONNECT tunnel requests, allowing unauthenticated clients to bypass credential requirements. Attackers can issue CONNECT requests to establish tunnels through the authenticated proxy without providing credentials, enabling arbitrary TCP traffic relay and access to restricted destinations.

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