---
id: CVE-2026-48521
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 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy's
  ProdClusterManagerFactory::allocateConnPool dereferences
  transport_socket_options while selectin…
severity: medium
cvss: 5.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-476
vendor: envoyproxy
product: envoy
affected:
  - envoy < 1.36.10
  - 'envoy >= 1.37.0, < 1.37.6'
  - 'envoy >= 1.38.0, < 1.38.4'
  - 'envoy >= 1.39.0, < 1.39.1'
published: '2026-09-21'
updated: '2026-09-23'
sourceUpdated: '2026-09-23T18:12:04.247'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-48521'
references:
  - url: >-
      https://github.com/envoyproxy/envoy/commit/8ef2da8527fcd17388b046c1add4fb47fb5d0868
    label: security-advisories@github.com
  - url: >-
      https://github.com/envoyproxy/envoy/commit/cec4899acf03cf551f28611a5f32385648d95f96
    label: security-advisories@github.com
  - url: >-
      https://github.com/envoyproxy/envoy/commit/e7b4839beef7f43594ce8e94c4563c80db04a8a7
    label: security-advisories@github.com
  - url: >-
      https://github.com/envoyproxy/envoy/commit/f5436f44103fb14cb8ba42a8db0f54a06c98c45a
    label: security-advisories@github.com
  - url: 'https://github.com/envoyproxy/envoy/releases/tag/v1.36.10'
    label: security-advisories@github.com
  - url: 'https://github.com/envoyproxy/envoy/releases/tag/v1.37.6'
    label: security-advisories@github.com
  - url: 'https://github.com/envoyproxy/envoy/releases/tag/v1.38.4'
    label: security-advisories@github.com
  - url: 'https://github.com/envoyproxy/envoy/releases/tag/v1.39.1'
    label: security-advisories@github.com
  - url: >-
      https://github.com/envoyproxy/envoy/security/advisories/GHSA-5vff-j9p4-38j3
    label: security-advisories@github.com
  - url: >-
      https://github.com/envoyproxy/envoy/security/advisories/GHSA-5vff-j9p4-38j3
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-48521.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-48521'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2512093'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-48521'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-48521'
tags:
  - nvd
  - cve.org
  - exploit-available
  - csaf
  - vex
  - red-hat
epss: 0.00699
epssPercentile: 0.51119
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-21T20:02:39.214503Z'
ingestedAt: '2026-09-21T19:51:58.868Z'
---

## Overview

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy's ProdClusterManagerFactory::allocateConnPool dereferences transport_socket_options while selecting an HTTP/3 connection pool without first checking whether the pointer is null. LoadBalancerContext implementations used by synthetic, mirror, health-check, and async-client calls can return no transport-socket options. With auto_config and HTTP/3 enabled, routine traffic reaching one of those contexts can crash an Envoy worker. The relevant scope boundary is that the affected branch requires HTTP/3 in the protocol set and a context that supplies no transport-socket options. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · Moderate · updated 2026-09-22 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-48521.json)