Vulnerability · Published Mar 20, 2026 · Assigned by GitHub_M

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

Medium 6.3

In plain English

A medium-severity security flaw in traefik from traefik. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 35% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)6.3Medium

Exploit odds (30 days)0.4%top 65.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Go	github.com/traefik/traefik	no fix listed	GO-2026-4792
Go	github.com/traefik/traefik	no fix listed	GHSA-g3hg-j4jv-cwfr
Go	github.com/traefik/traefik/v2	2.11.41	GO-2026-4792
Go	github.com/traefik/traefik/v2	2.11.41	GHSA-g3hg-j4jv-cwfr
Go	github.com/traefik/traefik/v3	3.7.0-ea.2	GHSA-g3hg-j4jv-cwfr
Go	github.com/traefik/traefik/v3	3.6.11	GHSA-g3hg-j4jv-cwfr
Go	github.com/traefik/traefik/v3	3.6.11, 3.7.0-ea.2	GO-2026-4792

Affected products (as reported)

Vendor	Product	Versions
traefik	traefik	< 2.11.41>= 3.0.0-beta1, < 3.6.11>= 3.7.0-ea.1, < 3.7.0-ea.2

Weakness: CWE-208 · 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

References

https://github.com/traefik/traefik/security/advisories/GHSA-g3hg-j4jv-cwfr x_refsource_CONFIRM
https://github.com/traefik/traefik/releases/tag/v2.11.41 x_refsource_MISC
https://github.com/traefik/traefik/releases/tag/v3.6.11 x_refsource_MISC
https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.2 x_refsource_MISC