6.3

CVE-2026-41263: Traefik: BasicAuth middleware: timing side-channel vulnerability

Analyzed
AliasesGHSA-6x2q-h3cr-8j2hGO-2026-5195CGA-435f-2j66-mf8x
Published 30-04-2026Last modified 01-05-2026

Vulnerability summary

CVE-2026-41263 is a medium (CVSS 6.3) Observable Timing Discrepancy vulnerability in traefik. EPSS estimates a 0.37% chance of exploitation in the next 30 days, higher than 30.8% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 6.3, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
6.3/10
010
Medium · v4.0 (CVE.org)
EPSS score
0.37%
0%100%
Low · -0.04 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 3 · Related 3
OPENSUSE-SU-2026:10697-1OPENSUSE-SU-2026:10698-1OPENSUSE-SU-2026:21483-1

Timeline

  1. 30-04-2026
    PublishedVulnerability first disclosed.
  2. 01-05-2026
    Last modifiedVulnerability information updated.

Description

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.

CVSS metrics

6 scores · 4 sources · 2 versions

EPSS trend

Probability

0.37%

Chance of exploitation in the next 30 days

Percentile

31%

Versus all other CVEs

30-day change

Decrease -0.04 pp

From 0.41% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Chainguard2 products
  • traefik-3.5All versions (No fix recorded)
  • traefik-fips-3.5All versions (No fix recorded)
Github.com/traefik/traefik2 products
  • v2< 2.11.43
  • v3≥ 3.0.0-beta1, < 3.6.14 | ≥ 3.7.0-ea.1, < 3.7.0-rc.2
Github.com/traefik1 product
  • traefik≤ 1.7.34 | All versions (No fix recorded)
Traefik1 product
  • traefik≥ 3.0.0-beta1, < 3.6.14 | ≥ 3.7.0-ea.1, < 3.7.0-rc.2 | < 2.11.43 | ≥ 3.0.0, < 3.6.14 | 3.7.0:ea1 | 3.7.0:ea2 | 3.7.0:ea3 | 3.7.0:rc1

4 vendors · 6 products

References

7 links