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CVE-2026-33433

nvd nist
Published: Mar 27, 2026Modified: Jul 15, 2026

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5.1
Vector
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/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
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CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/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:XShow less
Source: security-advisories@github.com (Secondary)

Description

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.42, 3.6.11, and 3.7.0-ea.3, when `headerField` is configured with a non-canonical HTTP header name (e.g., `x-auth-user` instead of `X-Auth-User`), an authenticated attacker can inject their own canonical version of that header to impersonate any identity to the backend. The backend receives two header entries — the attacker-injected canonical one is read first, overriding Traefik's non-canonical write. Versions 2.11.42, 3.6.11, and 3.7.0-ea.3 patch the issue.

Affected (4)

Products: Traefik: Traefik
Traefik
1 product
Traefik
Configuration A
4 vulnerable
Vulnerable SoftwareAffected Versions
Traefik
Traefik
Before 2.11.42
Traefik
From 3.0.0 to 3.6.12
Traefik
Version 3.7.0 ea1
Traefik
Version 3.7.0 ea2

Related CWEs

CWE-290
Authentication Bypass by Spoofing
This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.

References (8)

Source: security-advisories@github.com
ProductRelease Notes
Source: security-advisories@github.com
ProductRelease Notes
Source: security-advisories@github.com
ProductRelease Notes
Source: security-advisories@github.com
ExploitPatchVendor Advisory
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

Timeline

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