CVE-2026-108334: Kuadrant Operator Auth Bypass Vulnerability

CVE-2026-108334 Overview

CVE-2026-108334 is a code injection flaw in the internal WebAssembly (WASM) shim used by the Kuadrant operator. The shim generates Common Expression Language (CEL) predicates that decide whether Gateway-level authentication and rate limiting should run for a request. It fails to escape values taken from HTTPRoute match fields when building those predicates. An authenticated user who can create or modify an HTTPRoute attached to a shared Gateway can supply crafted path, header, or query match values that cause the predicate to skip enforcement. Requests are still forwarded to the backend, bypassing authentication and rate limiting controls. The weakness is tracked under CWE-917 (Improper Neutralization of Special Elements used in an Expression Language Statement).

Critical Impact
Tenants sharing a Kuadrant-managed Gateway can bypass authentication and rate limiting on protected routes by injecting crafted match values into HTTPRoute resources.

Affected Products

Kuadrant Operator (internal WASM shim component)
Red Hat Connectivity Link (per RHSA-2026:83531)
Red Hat Connectivity Link (per RHSA-2026:88203)

Discovery Timeline

2026-10-15 - CVE-2026-108334 published to NVD
2026-10-23 - Last updated in NVD database

Technical Details for CVE-2026-108334

Vulnerability Analysis

Kuadrant extends Kubernetes Gateway API resources with policies for authentication (AuthPolicy) and rate limiting (RateLimitPolicy). To enforce those policies at the data plane, the Kuadrant operator generates CEL predicates that an Envoy WASM extension evaluates per request. These predicates inspect route match criteria such as paths, headers, and query parameters to determine which policy should apply.

The operator constructs CEL expressions by concatenating untrusted strings from HTTPRoute match fields directly into the predicate source. Because those values are not escaped or quoted safely, an attacker who controls an HTTPRoute can inject CEL syntax that alters the predicate logic. The injected expression can evaluate to a condition that causes the shim to skip authentication and rate limiting while the request continues to the backend. The impact is limited to tenants who already have permission to create or modify HTTPRoute resources attached to a shared Gateway, which is why the CVSS vector requires low privileges rather than none.

Root Cause

The root cause is improper neutralization of expression language input (CWE-917). The Kuadrant operator treats HTTPRoute match values as trusted data when building CEL predicates, instead of escaping metacharacters or using safe parameter binding. Any CEL operator or literal supplied through a match value becomes part of the predicate grammar.

Attack Vector

The attack is launched over the network against the Kubernetes API by any principal with permission to create or modify HTTPRoute resources on a Kuadrant-managed Gateway. The attacker crafts a path, header, or query match that embeds CEL syntax. When the operator reconciles the route, it emits a predicate that evaluates to false for the authentication and rate limiting hooks. Subsequent requests that match the route bypass the Gateway-level AuthPolicy and RateLimitPolicy and are forwarded to the configured backend. The fix is applied in commit 7e667dc of the Kuadrant operator.

No verified public proof-of-concept is available. See the GitHub Security Advisory GHSA-fcw2-f6v9-6ffp for the maintainers' technical description.

Detection Methods for CVE-2026-108334

Indicators of Compromise

HTTPRoute resources whose spec.rules[].matches[] fields contain CEL metacharacters such as ||, &&, !, quotes, or parentheses in path, header, or query values.
Backend access logs showing requests to protected routes with no corresponding entries in the Kuadrant authentication or rate limiting audit logs.
Reconciliation events on the Kuadrant operator referencing newly modified HTTPRoute resources attached to shared Gateways.

Detection Strategies

Compare generated WASM shim configuration (CEL predicates) against the originating HTTPRoute match values and alert on predicates containing operators not derivable from the input.
Enable Kubernetes audit logging for httproutes.gateway.networking.k8s.io and flag create or update events that introduce non-standard characters in match fields.
Correlate Envoy access logs with Kuadrant Authorino and Limitador decision logs to surface requests that reached backends without an enforcement decision.

Monitoring Recommendations

Monitor rate limiting counters per route and alert on sudden drops that indicate policy skipping rather than reduced traffic.
Track authentication failure and success ratios per HTTPRoute; routes with traffic but zero authentication decisions warrant review.
Review RBAC bindings granting HTTPRoute write access on shared Gateways and audit changes continuously.

How to Mitigate CVE-2026-108334

Immediate Actions Required

Upgrade the Kuadrant operator to a release that includes commit 7e667dc.
Apply the Red Hat Connectivity Link updates in RHSA-2026:83531 and RHSA-2026:88203.
Audit existing HTTPRoute resources on shared Gateways for suspicious match values and revert unexpected changes.
Restrict RBAC so that only trusted service accounts can create or modify HTTPRoute resources attached to Kuadrant-managed Gateways.

Patch Information

The upstream fix is published in the Kuadrant operator repository and shipped by Red Hat through RHSA-2026:83531 and RHSA-2026:88203. Additional vendor context is available in the Red Hat CVE record and Bugzilla #2548768.

Workarounds

Use dedicated Gateways per tenant instead of shared Gateways until the operator is patched.
Enforce an admission policy (for example, Kyverno or Gatekeeper) that rejects HTTPRoute match values containing CEL metacharacters.
Apply backend-side authentication as a defense-in-depth control so that bypassing the Gateway policy does not grant unauthenticated access.