Traefik: Kubernetes Gateway crossProviderNamespaces bypass allows HTTPRoute outside the allowlist to expose internal Traefik services

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Summary

CVECVE-2026-54761
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-23 20:16:49 UTC
Updated2026-06-23 20:16:49 UTC
DescriptionTraefik is an HTTP reverse proxy and load balancer. Prior to 3.6.21 and 3.7.5, there is a high severity vulnerability in Traefik's Kubernetes Gateway provider affecting the crossProviderNamespaces allowlist. For HTTPRoute rules that declare multiple (WRR) backendRefs, Traefik evaluates the allowlist against the target backendRef.namespace instead of the route's own namespace. As a result, an HTTPRoute created in a namespace that is not allow-listed can reference a cross-provider TraefikService such as api@internal, dashboard@internal or rest@internal by pointing backendRef.namespace at an allow-listed namespace covered by a Gateway API ReferenceGrant, exposing internal Traefik services on the data plane. Exploitation requires the ability to create an accepted HTTPRoute and a matching ReferenceGrant from an allow-listed namespace; it does not require any change to Traefik static configuration, RBAC, or the deployment itself. This vulnerability is fixed in 3.6.21 and 3.7.5.

Risk And Classification

Primary CVSS: v4.0 6 MEDIUM from [email protected]

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/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-284 | CWE-863 | CWE-284 CWE-284: Improper Access Control | CWE-863 CWE-863: Incorrect Authorization

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary6MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/C...
4.0CNADECLARED6MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N

CVSS v4.0 Breakdown

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

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/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 < 3.6.21 Not specified
CNA Traefik Traefik affected >= 3.7.0-ea.1, < 3.7.5 Not specified

References

ReferenceSourceLinkTags
github.com/traefik/traefik/releases/tag/v3.6.21 [email protected] github.com
github.com/traefik/traefik/releases/tag/v3.7.5 [email protected] github.com
github.com/traefik/traefik/security/advisories/GHSA-3g6v-2r68-prfc [email protected] github.com
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