---
id: CVE-2026-47774
title: >-
  Envoy is an open source edge and service proxy designed for cloud-native
  applications
summary: >-
  Envoy is an open source edge and service proxy designed for cloud-native
  applications. Prior to versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a
  vulnerability in Envoy's HTTP/2 downstream request processing allows an
  unauthenticated remot…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-405
  - CWE-770
  - CWE-409
vendor: envoyproxy
product: envoy
affected:
  - envoy < 1.35.11
  - 'envoy >= 1.36.0, < 1.36.7'
  - 'envoy >= 1.37.0, < 1.37.3'
  - envoy = 1.38.0
  - 'openshift_service_mesh >= 2.6, < 2.6.17'
  - 'openshift_service_mesh >= 3.0, < 3.0.12'
  - 'openshift_service_mesh >= 3.1, < 3.1.9'
  - 'openshift_service_mesh >= 3.2, < 3.2.6'
  - 'openshift_service_mesh >= 3.3, < 3.3.4'
patched:
  - envoy 1.37.3
  - openshift_service_mesh 3.3.4
published: '2026-06-17'
updated: '2026-07-06'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-47774'
references:
  - url: >-
      https://github.com/envoyproxy/envoy/security/advisories/GHSA-22m2-hvr2-xqc8
    label: security-advisories@github.com
  - url: 'http://www.openwall.com/lists/oss-security/2026/06/04/15'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/errata/RHSA-2026:26210'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26222'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26231'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:26247'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:27114'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/security/cve/CVE-2026-47774'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2487465'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-47774.json
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
tags:
  - nvd
epss: 0.01052
epssPercentile: 0.62863
ingestedAt: '2026-07-06T17:44:51.200Z'
---

## Overview

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a vulnerability in Envoy's HTTP/2 downstream request processing allows an unauthenticated remote client to trigger excessive memory consumption, potentially resulting in OOM termination of the Envoy process and denial of service. The issue arises from the combination of two behaviors. First, cookie header bytes are not fully accounted for during request header size validation in Envoy. Second, HPACK header block limits in oghttp2/quiche are enforced on encoded bytes without a corresponding limit on total decoded header size. Together, these behaviors allow a malicious client to cause large decoded header allocations while bypassing the intended request header size protections. Versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1 contain a fix. No complete workaround is known short of applying a fix. Possible temporary mitigations include disabling downstream HTTP/2 where operationally feasible; enforcing stricter request header and cookie limits before traffic reaches Envoy; and monitoring Envoy memory usage for abnormal growth under HTTP/2 traffic.

## Affected

- `envoy < 1.35.11`
- `envoy >= 1.36.0, < 1.36.7`
- `envoy >= 1.37.0, < 1.37.3`
- `envoy = 1.38.0`
- `openshift_service_mesh >= 2.6, < 2.6.17`
- `openshift_service_mesh >= 3.0, < 3.0.12`
- `openshift_service_mesh >= 3.1, < 3.1.9`
- `openshift_service_mesh >= 3.2, < 3.2.6`
- `openshift_service_mesh >= 3.3, < 3.3.4`

## Remediation

Upgrade past the affected range:

- `envoy 1.37.3`
- `openshift_service_mesh 3.3.4`