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BIT-envoy-2026-26308 — Envoy has an RBAC Header Validation Bypass via Multi-Value Header Concatenation

Affected: Bitnami: envoy

Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, the Envoy RBAC (Role-Based Access Control) filter contains a logic vulnerability in how it validates HTTP headers when multiple values are present for the same header name. Instead of validating each header value individually, Envoy concatenates all values into a single comma-separated string. This behavior allows attackers to bypass RBAC policies—specifically "Deny" rules—by sending duplicate headers, effectively obscuring the malicious value from exact-match mechanisms. This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13.

EUVD-2026-275357

fkie_cve-2026-26308

GHSA-ghc4-35x6-crw5 — Envoy has RBAC Header Validation Bypass via Multi-Value Header Concatenation

Affected: Go: github.com/envoyproxy/envoy

## 1. Summary The Envoy RBAC (Role-Based Access Control) filter contains a logic vulnerability in how it validates HTTP headers when multiple values are present for the same header name. Instead of validating each header value individually, Envoy concatenates all values into a single comma-separated string. This behavior allows attackers to bypass RBAC policies—specifically "Deny" rules—by sending duplicate headers, effectively obscuring the malicious value from exact-match mechanisms.

## 2. Attack Scenario Consider an environment where an administrator wants to block external access to internal resources using a specific header flag.

### Configuration The Envoy proxy is configured with a **Deny** rule to reject requests containing the header `internal: true`. * **Rule Type:** Exact Match * **Target:** `internal` header must not equal `true`.

### The Bypass Logic 1. **Standard Request (Blocked):** * **Input:** `internal: true` * **Envoy Processing:** Sees string `"true"`. * **Result:** Match found. **Request Denied.**

2. **Exploit Request (Bypassed):** * **Input:** ```http internal: true internal: true ``` * **Envoy Processing:** Concatenates values into `"true,true"`. * **Matcher Evaluation:** Does `"true,true"` equal `"true"`? **No.** * **Result:** The Deny rule fails to trigger. **Request Allowed.**

## 3. Implications * **RBAC Bypass:** Remote attackers can bypass configured access controls. * **Unauthoriz…

WID-SEC-W-2026-0704 — Google Cloud Platform Envoy Proxy, Istio und Service Mesh: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Google Cloud Platform ausnutzen, um Sicherheitsvorkehrungen zu umgehen, vertrauliche Informationen offenzulegen oder einen Denial-of-Service-Zustand zu verursachen.