GHSA-5m6w-wvh7-57vm: github.com/traefik/traefik/v3 (CVE-2026-39858)

Traefik: Pre-authentication decision bypass due to forwarded alias spoofing

CVSS 7.8 HighEPSS 0.0048 · 41st percentile

Published by the GitHub Advisory Database at 24 Apr 2026, 16:32 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

Package	Ecosystem	Affected	Fixed in
github.com/traefik/traefik/v3	Go	>=3.7.0-ea.1, <3.7.0-rc.2 \|\| >=3.0.0-beta1, <3.6.14	3.7.0-rc.2, 3.6.14
github.com/traefik/traefik/v2	Go	<2.11.43	2.11.43
github.com/traefik/traefik	Go	<=1.7.34	No fixed version yet

Identifiers

GHSA-5m6w-wvh7-57vm · CVE-2026-39858 · GO-2026-5149

Weakness (CWE)

CWE-289 · CWE-290 · CWE-306

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

Score	Rating	CVSS	Vector	Source
7.8	High	4.0	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	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0048, the 41st percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 15:07 UTC First seen by agentprime
31 Oct 2026, 15:07 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.