CVE-2026-41263
Description
A flaw was found in Traefik. A remote attacker can exploit a timing side-channel vulnerability in Traefik's BasicAuth middleware. This flaw allows an attacker to enumerate valid usernames by observing differences in authentication response times. The vulnerability arises because a constant-time comparison, intended to prevent such attacks, short-circuits, revealing whether a username exists.
Mitigation
To mitigate this issue, restrict network access to Traefik instances that utilize the BasicAuth middleware. Implement firewall rules or network access controls to limit connections to trusted networks or clients only. This reduces the exposure to remote attackers attempting username enumeration. Always ensure that any changes to network configurations are thoroughly tested to prevent service disruption. A service reload or restart may be required for changes to take effect.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.3 | 3.7 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | High | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | Low | Low | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | None | None | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
NVD: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Understanding the Weakness (CWE)
Confidentiality,Access Control
Technical Impact: Read Application Data; Bypass Protection Mechanism
Frequently Asked Questions
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