CVE-2026-54765: Traefik Gateway API Filter Isolation Bypass – Privilege Escalation Risk

Technical summary

The vulnerability stems from improper filter context isolation when the Gateway API provider resolves multiple HTTPRoutes that share the same backend Service:port but differ in their backendRef filter configurations. The implementation applies only one filter set to all matching requests, creating a collision where a lower-priority or attacker-controlled route's filters override or replace the intended filters. This occurs within the Kubernetes control plane context, where namespace isolation can be breached if cross-namespace ReferenceGrants are configured. The issue affects CWE-284 (Improper Access Control) and CWE-863 (Incorrect Authorization), allowing security headers and context to leak across route boundaries.

Business impact

Organizations running Traefik 3.7.0–3.7.5 as a Kubernetes ingress or gateway controller face significant risk if multi-tenant or security-sensitive routing policies depend on per-route filter isolation. An insider or compromised pod with create privileges on HTTPRoutes could inject malicious filters that apply to other tenants' traffic, potentially exposing authorization tokens, user identity headers, or tenant context to unauthorized parties. In regulated environments, this could violate data residency, compliance, or segregation requirements. The impact is amplified in shared Kubernetes clusters where untrusted workloads coexist.

Affected systems

Traefik versions 3.7.0, 3.7.1, 3.7.2, 3.7.3, 3.7.4, and 3.7.5 are affected when deployed as a Kubernetes Gateway API provider. Version 3.7.6 and later contain the fix. Users on earlier v3.x or v2.x series are not affected by this specific issue. The vulnerability is only exposed in Kubernetes environments using the Gateway API (not legacy Ingress resources). Non-Kubernetes deployments of Traefik are unaffected.

Exploitability

Exploitation requires PR:L (Privilege Level: Low)—the attacker must have authenticated Kubernetes API access with permissions to create or modify HTTPRoute resources. They do not require code execution or network-level manipulation. Once an HTTPRoute is accepted by the controller, the filter collision occurs automatically without user interaction (UI:N). The attack is deterministic and can be triggered repeatedly. The low barrier to entry for cluster-internal attackers or pod operators with API permissions makes this a moderate-to-high practical risk in environments with permissive RBAC policies.

Remediation

Upgrade Traefik to version 3.7.6 or later. Organizations unable to upgrade immediately should audit RBAC policies to restrict HTTPRoute creation and modification to trusted administrators, implement network policies to isolate Traefik control plane traffic, and review existing HTTPRoute configurations for multi-tenant deployments. If cross-namespace ReferenceGrants are in use, evaluate whether they can be narrowed or removed pending patching.

Patch guidance

Apply Traefik v3.7.6 or a later v3.7.x or v3.x release. Verify the fix by reviewing the release notes for the filter isolation correction. Test in a non-production Kubernetes environment to confirm HTTPRoute filter contexts remain isolated after upgrade. Monitor for any custom or third-party Gateway API providers in use alongside Traefik; validate their filter handling independently.

Detection guidance

Monitor Kubernetes audit logs for repeated HTTPRoute creation or modification events by non-admin service accounts or users. Check for requests to backend Services where the Authorization, X-Tenant-ID, or other security-sensitive headers differ unexpectedly between routes targeting the same Service:port. Review Gateway API provider logs for warnings or errors related to filter conflicts. Implement admission controllers or network policies to flag or block HTTPRoute resources with overlapping backend targets but differing filters.

Why prioritize this

CVSS 8.5 (HIGH) combined with the vulnerability's ability to cross namespace boundaries, impact on authorization/identity headers, and the low barrier to exploitation for cluster-internal actors makes this a priority fix. The vulnerability directly undermines Kubernetes multi-tenancy and security isolation assumptions. Organizations with shared clusters or untrusted workloads should prioritize patching within 30 days.

Risk score, explained

The score reflects network accessibility within the cluster (AV:N), low attack complexity (AC:L), and the requirement for low privilege (PR:L). The scope change (S:C) indicates potential impact beyond the Traefik component (affecting backend services and tenants). Confidentiality is rated Low (C:L) because header leakage is typically partial; Integrity is High (I:H) because attackers can inject or override security-sensitive context; Availability is None (A:N) as the vulnerability does not degrade service.

Frequently asked questions