CVSS 4.0
6.3 mediumCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:NCVE-2026-41263
Medium (6.3) in traefik traefik. EPSS 0.4% chance of exploitation in the next 30 days. Fixed in github.com/traefik/traefik/v3 3.6.14, 3.7.0-rc.2.
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.
Severity
CVSS 3.1
3.7 lowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N- EPSS
- 0.4% chance of exploitation in the next 30 days; higher than 30% of CVEs (scores of 2026-10-31)
- CWE
- CWE-208
- Published
- Modified
- Record from
- the NVD, synced
Affected
- traefik:traefik
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-6x2q-h3cr-8j2h | Go | github.com/traefik/traefik/v3 | >=3.7.0-ea.1 <3.7.0-rc.2 | 3.7.0-rc.2 |
| GHSA-6x2q-h3cr-8j2h | Go | github.com/traefik/traefik/v3 | >=3.0.0-beta1 <3.6.14 | 3.6.14 |
| GHSA-6x2q-h3cr-8j2h | Go | github.com/traefik/traefik/v2 | <2.11.43 | 2.11.43 |
| GHSA-6x2q-h3cr-8j2h | Go | github.com/traefik/traefik | <=1.7.34 | no fix published |
| GO-2026-5195 | Go | github.com/traefik/traefik | all versions | no fix published |
| GO-2026-5195 | Go | github.com/traefik/traefik/v2 | <2.11.43 | 2.11.43 |
| GO-2026-5195 | Go | github.com/traefik/traefik/v3 | >=3.0.0-beta1 <3.6.14 >=3.7.0-ea.1 <3.7.0-rc.2 | 3.6.14, 3.7.0-rc.2 |