CVE-2026-26308

HIGH EPSS 21.0%
Published Mar 10, 20263mo ago · Modified Jun 17, 20261w ago
8.2 CVSS 3.1
High
Find Similar
Published Mar 10, 2026 3mo ago
Last Modified Jun 17, 2026 1w ago

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.

CVSS Details

Base Score
8.2
Exploitability
3.9
Impact
4.2
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope Unchanged
Confidentiality High
Integrity Low
Availability None

Threat Intelligence

EPSS Exploit Probability
21.0% percentile
Exploit & Patch Status
Public Exploit Known
Patch Available

Weaknesses 1

CWE-863 Incorrect Authorization Authorization

Affected Products 4

VendorProductVersionRange
envoyproxyenvoy* <1.34.13
envoyproxyenvoy*≥1.35.0  –  <1.35.8
envoyproxyenvoy*≥1.36.0  –  <1.36.5
envoyproxyenvoy1.37.0any

References 2

  • github.com https://github.com/envoyproxy/envoy/commit/b6ba0b2294b98484fb0ed8556897d1073cc27867
    Patch
  • github.com https://github.com/envoyproxy/envoy/security/advisories/GHSA-ghc4-35x6-crw5
    ExploitMitigationVendor Advisory

Remediation

  • github.com https://github.com/envoyproxy/envoy/commit/b6ba0b2294b98484fb0ed8556897d1073cc27867
    Patch