# CVE-2026-41263

> Vulnerability · severity: **LOW** (CVSS 3.7).

## 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.

## Key facts

- **CVE ID:** CVE-2026-41263
- **Published:** 2026-04-30
- **CVSS severity:** LOW
- **CVSS base score:** 3.7
- **CWE codes:** CWE-208

## Affected products

- `traefik:traefik`

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-41263

## Citation

> AI Analytics. CVE-2026-41263. Retrieved 2026-07-03 from https://api.ai-analytics.org/cve/CVE-2026-41263. Derived from NIST NVD. Licensed CC0.

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