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© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2026-41263

21
FAUCET Score

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a timing side-channel vulnerability in Traefik's BasicAuth middleware that allows an attacker to enumerate valid usernames through response-time differences. The variable intended to hold a constant-time fallback secret always resolves to an empty string, causing the constant-time comparison to short-circuit in microseconds rather than performing a full bcrypt evaluation. This restores the original timing oracle and makes it possible to distinguish existing users from non-existing ones by measuring authentication response times. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2.

First published: Apr 30, 2026Last modified: May 1, 2026

Impacted Technologies

VendorProductVersion(s)CPE
< 2.11.43CPE matchmatch criteria
cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*
>= 3.0.0, < 3.6.14CPE matchmatch criteria
cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*
3.7.0CPE matchmatch criteria
cpe:2.3:a:traefik:traefik:3.7.0:ea1:*:*:*:*:*:*
3.7.0CPE matchmatch criteria
cpe:2.3:a:traefik:traefik:3.7.0:ea2:*:*:*:*:*:*
3.7.0CPE matchmatch criteria
cpe:2.3:a:traefik:traefik:3.7.0:ea3:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 4.0

6.3MEDIUM

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector
NETWORK
Attack Complexity
HIGH
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
VS Confidentiality
NONE
VS Integrity
NONE
VS Availability
NONE
SS Confidentiality
LOW
SS Integrity
NONE
SS Availability
NONE
Exploit Maturity
NOT_DEFINED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
0.37%
Probability of exploitation in next 30 days
EPSS Percentile
29.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0037 is in the 18th percentile among its peer group of 1,506 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.3 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (4)

github_advisorypatch availablevia nvd_reference
View patch
gopatch availablevia ghsa
Product: github.com/traefik/traefik/v3Fixed in: 3.7.0-rc.2
gopatch availablevia ghsa
Product: github.com/traefik/traefik/v3Fixed in: 3.6.14
gopatch availablevia ghsa
Product: github.com/traefik/traefik/v2Fixed in: 2.11.43

Vendor Advisories (1)

goGHSA-6x2q-h3cr-8j2hmedium

Traefik: A timing side-channel vulnerability allows for valid username enumeration via BasicAuth middleware

Apr 24, 2026

References

github.com / traefik/traefik/releases/tag/v2.11.43
ProductRelease Notes
github.com / traefik/traefik/releases/tag/v3.6.14
ProductRelease Notes
github.com / traefik/traefik/releases/tag/v3.7.0-rc.2
ProductRelease Notes
github.com / traefik/traefik/security/advisories/GHSA-6x2q-h3cr-8j2h
PatchVendor Advisory