---
cve: "CVE-2026-41263"
severity: "MEDIUM"
cvss: 6.3
epss: "37%"
vendor: "traefik"
kev: false
exploited: false
published: "2026-04-30 21:16:33"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-09-19T08:41:01+02:00"
---

# CVE-2026-41263

> 6.3 MEDIUM · 🧪 PoC

## Beschreibung

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-Vektor

```
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
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Hoch | good |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Patch verfügbar (OSV)

- a9ce32a8dc3db5170e283215ab000bd053aea865 (Commit)
- a6664c95b589842489d37d73e7d01bf1c8881685 (Commit)

## Referenzen

- <https://github.com/traefik/traefik/security/advisories/GHSA-6x2q-h3cr-8j2h>
- <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>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-41263) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_