CVE-2026-33433
Description
A flaw was found in Traefik, an HTTP reverse proxy and load balancer. When the headerField is configured with a non-canonical HTTP header name, an authenticated attacker can inject a canonical version of that header. This allows the attacker to impersonate any identity to the backend, leading to an authentication bypass. The backend prioritizes the attacker-injected header, overriding Traefik's intended header.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
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).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.7 | 8.8 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | High | Low | N/A |
| Privileges Required | High | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Changed | Unchanged | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | None | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Access Control
Technical Impact: Bypass Protection Mechanism; Gain Privileges or Assume Identity
This weakness can allow an attacker to access resources which are not otherwise accessible without proper authentication.
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