Vulnerability CVE-2026-41263: Information
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.
Severity: MEDIUM (6.3)
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/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
Severity: LOW (3.7)
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Fixed packages
Package name | Branch | Fixed in version | Version from repository | Errata ID | Task # | State |
|---|---|---|---|---|---|---|
| traefik | sisyphus | 3.6.15-alt1 | 3.6.15-alt1 | ALT-PU-2026-7142-5 | 417190 | Fixed |
| traefik | sisyphus_riscv64 | 3.6.15-alt1 | 3.6.15-alt1 | ALT-PU-2026-7534-1 | - | Fixed |
| traefik | sisyphus_loongarch64 | 3.6.15-alt1 | 3.6.15-alt1 | ALT-PU-2026-7499-1 | - | Fixed |
| traefik | p11 | 3.6.15-alt1 | 3.6.15-alt1 | ALT-PU-2026-7164-5 | 417230 | Fixed |
| traefik | c10f2 | 3.6.15-alt1 | 3.6.15-alt1 | ALT-PU-2026-7154-5 | 417229 | Fixed |
References to Advisories, Solutions, and Tools
Hyperlink | Resource |
|---|---|
| https://github.com/traefik/traefik/releases/tag/v2.11.43 |
|
| https://github.com/traefik/traefik/releases/tag/v3.6.14 |
|
| https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2 |
|
| https://github.com/traefik/traefik/security/advisories/GHSA-6x2q-h3cr-8j2h |
|
| GHSA-6x2q-h3cr-8j2h |