CVE-2026-33433

MEDIUM EPSS 35.9%
Published Mar 27, 20263mo ago · Modified Jun 17, 20261w ago
5.1 CVSS 4.0
Medium
Find Similar
Published Mar 27, 2026 3mo ago
Last Modified Jun 17, 2026 1w ago

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.

CVSS Details

Base Score
5.1
Exploitability
—
Impact
—
Vector string
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
Attack Vector Network
Attack Complexity High
Privileges Required High
User Interaction None
Scope X

Threat Intelligence

EPSS Exploit Probability
35.9% percentile
Exploit & Patch Status
Public Exploit Known
Patch Available

Weaknesses 1

CWE-290

Affected Products 4

VendorProductVersionRange
traefiktraefik* <2.11.42
traefiktraefik*≥3.0.0  –  <3.6.12
traefiktraefik3.7.0any
traefiktraefik3.7.0any

References 4

  • github.com https://github.com/traefik/traefik/releases/tag/v2.11.42
    ProductRelease Notes
  • github.com https://github.com/traefik/traefik/releases/tag/v3.6.11
    ProductRelease Notes
  • github.com https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3
    ProductRelease Notes
  • github.com https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c
    ExploitPatchVendor Advisory

Remediation

  • github.com https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c
    ExploitPatchVendor Advisory