CVE-2026-33433
Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField
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.
INFO
Published Date :
March 27, 2026, 3:16 p.m.
Last Modified :
April 3, 2026, 5:09 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update Traefik to version 2.11.42 or later.
- Update Traefik to version 3.6.11 or later.
- Update Traefik to version 3.7.0-ea.3 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-33433.
| URL | Resource |
|---|---|
| https://github.com/traefik/traefik/releases/tag/v2.11.42 | Product Release Notes |
| https://github.com/traefik/traefik/releases/tag/v3.6.11 | Product Release Notes |
| https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3 | Product Release Notes |
| https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c | Exploit Patch Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-33433 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-33433
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-33433 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-33433 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Apr. 03, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Added CPE Configuration OR *cpe:2.3:a:traefik:traefik:3.7.0:ea1:*:*:*:*:*:* *cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:* versions up to (excluding) 2.11.42 *cpe:2.3:a:traefik:traefik:3.7.0:ea2:*:*:*:*:*:* *cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:* versions from (including) 3.0.0 up to (excluding) 3.6.12 Added Reference Type GitHub, Inc.: https://github.com/traefik/traefik/releases/tag/v2.11.42 Types: Product, Release Notes Added Reference Type GitHub, Inc.: https://github.com/traefik/traefik/releases/tag/v3.6.11 Types: Product, Release Notes Added Reference Type GitHub, Inc.: https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3 Types: Product, Release Notes Added Reference Type GitHub, Inc.: https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c Types: Exploit, Patch, Vendor Advisory -
New CVE Received by [email protected]
Mar. 27, 2026
Action Type Old Value New Value Added 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. Added CVSS V4.0 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 Added CWE CWE-290 Added Reference https://github.com/traefik/traefik/releases/tag/v2.11.42 Added Reference https://github.com/traefik/traefik/releases/tag/v3.6.11 Added Reference https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3 Added Reference https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c