Traefik up to 2.11.55/3.7.11 Header Normalization improper authentication

Summaryinfo

A vulnerability classified as critical has been found in Traefik up to 2.11.55/3.7.11. Impacted is an unknown function of the component Header Normalization. This manipulation causes improper authentication. This vulnerability is handled as CVE-2026-88011. The attack can be initiated remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Traefik up to 2.11.55/3.7.11. Affected by this vulnerability is some unknown processing of the component Header Normalization. The manipulation with an unknown input leads to a improper authentication vulnerability. The CWE definition for the vulnerability is CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.56, and from 3.0.0 until 3.7.12, a client-supplied dot-form header such as X.Authenticated.User survives ForwardAuth replacement and underscoreHeadersStrategy because Go treats it as distinct from X-Authenticated-User while normalization-prone CGI, WSGI, PHP, and NGINX backends collapse both names. A backend can consequently consume the client value instead of the identity Traefik asserted, allowing identity spoofing for any header managed by Traefik. The aliasHeadersStrategy protection is disabled by default and must be configured as delete or reject. The mitigation is available in 2.11.56 and 3.7.12.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-88011 since 09/09/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available.

Upgrading to version 2.11.56 or 3.7.12 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Name

• Traefik

Version

• 2.11.0
• 2.11.1
• 2.11.2
• 2.11.3
• 2.11.4
• 2.11.5
• 2.11.6
• 2.11.7
• 2.11.8
• 2.11.9
• 2.11.10
• 2.11.11
• 2.11.12
• 2.11.13
• 2.11.14
• 2.11.15
• 2.11.16
• 2.11.17
• 2.11.18
• 2.11.19
• 2.11.20
• 2.11.21
• 2.11.22
• 2.11.23
• 2.11.24
• 2.11.25
• 2.11.26
• 2.11.27
• 2.11.28
• 2.11.29
• 2.11.30
• 2.11.31
• 2.11.32
• 2.11.33
• 2.11.34
• 2.11.35
• 2.11.36
• 2.11.37
• 2.11.38
• 2.11.39
• 2.11.40
• 2.11.41
• 2.11.42
• 2.11.43
• 2.11.44
• 2.11.45
• 2.11.46
• 2.11.47
• 2.11.48
• 2.11.49
• 2.11.50
• 2.11.51
• 2.11.52
• 2.11.53
• 2.11.54
• 2.11.55
• 3.7.0
• 3.7.1
• 3.7.2
• 3.7.3
• 3.7.4
• 3.7.5
• 3.7.6
• 3.7.7
• 3.7.8
• 3.7.9
• 3.7.10
• 3.7.11

Website

• Product: https://github.com/traefik/traefik/

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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