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.

Project Subscriptions

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-ghc4-35x6-crw5 Envoy has RBAC Header Validation Bypass via Multi-Value Header Concatenation
Fixes

Solution

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Workaround

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History

Tue, 10 Mar 2026 21:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 10 Mar 2026 19:30:00 +0000

Type Values Removed Values Added
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.
Title Envoy has an RBAC Header Validation Bypass via Multi-Value Header Concatenation
Weaknesses CWE-863
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-03-10T20:12:40.604Z

Reserved: 2026-02-13T16:27:51.804Z

Link: CVE-2026-26308

cve-icon Vulnrichment

Updated: 2026-03-10T20:11:58.525Z

cve-icon NVD

Status : Received

Published: 2026-03-10T20:16:35.707

Modified: 2026-03-10T20:16:35.707

Link: CVE-2026-26308

cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses