Traefik entrypoint header-name sanitization bypassed via request trailers

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-88004
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-10 15:17:54 UTC
Updated2026-09-10 16:18:07 UTC
DescriptionTraefik is an open source HTTP reverse proxy and load balancer. From 3.2.0 until 3.7.13, Traefik entrypoint defenses aliasHeadersStrategy, underscoreHeadersStrategy, and forwardedHeaders inspect req.Header but not req.Trailer, allowing an unauthenticated client to submit an aliasing or trusted header name in an HTTP/1.1 chunked trailer or an HTTP/2 trailer. When the retry or buffering middleware reads the body before the reverse proxy clones the request, the attacker-controlled trailer value reaches a backend that merges trailers into the header namespace, bypassing the documented delete or reject behavior and potentially spoofing identity or forwarded routing data. This issue is fixed in 3.7.13.

Risk And Classification

Primary CVSS: v4.0 7 HIGH from [email protected]

CVSS:4.0/AV:N/AC:H/AT:N/PR:N/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

Problem Types: CWE-436 | CWE-807 | CWE-436 CWE-436: Interpretation Conflict | CWE-807 CWE-807: Reliance on Untrusted Inputs in a Security Decision

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary7HIGHCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/C...
4.0CNADECLARED7HIGHCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
High
Attack Requirements
None
Privileges Required
None
User Interaction
None
Confidentiality
None
Integrity
None
Availability
None
Sub Conf.
High
Sub Integrity
High
Sub Availability
None

CVSS:4.0/AV:N/AC:H/AT:N/PR:N/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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Traefik Traefik affected >= 3.2.0, < 3.7.13 Not specified

References

ReferenceSourceLinkTags
github.com/traefik/traefik/releases/tag/v3.7.13 [email protected] github.com
github.com/traefik/traefik/security/advisories/GHSA-v67p-phpq-fc8x [email protected] github.com
github.com/traefik/traefik/pull/13822 [email protected] github.com
github.com/traefik/traefik/commit/55bbda4f65e0f9c533c870983a767a7081126db7 [email protected] github.com
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