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Advisory record · GHSA-8fcf-v89g-xpg6

Traefik: BasicAuth singleflight coalescing reintroduces an unauthenticated username-enumeration timing oracle

CVSS 6.3 MediumEPSS 0.0031 · 23rd percentile

Published by the GitHub Advisory Database at 22 Sept 2026, 20:40 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
github.com/traefik/traefik/v3Go>=3.6.11, <3.7.133.7.13
github.com/traefik/traefikGoall versionsNo fixed version yet
Identifiers
GHSA-8fcf-v89g-xpg6 · CVE-2026-88010 · GO-2026-6558
Weakness (CWE)
CWE-208
Tags
Published
22 Sept 2026
Updated
4 Nov 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Traefik versions 3.6.11 up to but not including 3.7.13 are affected. The BasicAuth middleware's singleflight key depends on whether a username exists, so an attacker who can send concurrent requests can enumerate valid usernames by timing responses, without credentials. The source gives no credential disclosure or authentication bypass. Upgrade to Traefik 3.7.13, which fixes the issue; v3.6 is end of life.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
6.3 Medium 4.0 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0031, the 23rd percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 22 Sept 2026, 20:40 UTC Confirmed by GitHub Advisory Database
  2. 31 Oct 2026, 14:12 UTC First seen by agentprime
  3. 31 Oct 2026, 14:12 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.