CVE-2026-26308

Severity CVSS v4.0:

Pending analysis

Type:

Unavailable / Other

Publication date:

10/03/2026

Last modified:

11/03/2026

Description

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.

Impact

Vector 3.x

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N CVSS v3.1 Severity and Metrics:

Base Score: 7.50 HIGH
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N

Attack Vector (AV): Network
Attack Complexity (AC): High
Privileges Required (PR): None
User Interaction (UI): None
Scope (S): Changed
Confidentiality (C): High
Integrity (I): Low
Availability (A): None

Base Score 3.x

7.50

Severity 3.x

HIGH

Vulnerable products and versions

CPE	From	Up to
cpe:2.3:a:envoyproxy:envoy::::::::		1.34.13 (excluding)
cpe:2.3:a:envoyproxy:envoy::::::::	1.35.0 (including)	1.35.8 (excluding)
cpe:2.3:a:envoyproxy:envoy::::::::	1.36.0 (including)	1.36.5 (excluding)
cpe:2.3:a:envoyproxy:envoy:1.37.0:::::::*

To consult the complete list of CPE names with products and versions, see this page

CVE-2026-26308

Description

Impact

Vulnerable products and versions

References to Advisories, Solutions, and Tools