Reference page — cumulative record through Thursday, October 8, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-48521

CVE-2026-48521MEDIUM

envoyproxy envoy — Envoy: HTTP/3 connection pool selection null-derefs in ProdClusterManagerFactory::allocateConnPool when transport_socket_options is null

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   H   N   N  U  N  N  H    5.9   .0074   53.1     —

AFFECTED
  Product  Versions     Fixed
  envoy    < 1.36.10 –  —

TIMELINE
  May 21  Reserved by GitHub_M
  Sep 21  Published (CNA: GitHub_M)
  Oct 5   EXPLOIT PUBLISHED — CVE-2026-48521 (envoyproxy envoy). Public exploit reference added.

CWE-476 · CNA: GitHub_M · CVSS v3.1 · 9 references · NVD status: Analyzed

Description

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
May 21, 2026	Reserved	Reserved by GitHub_M
September 21, 2026	Published	Published (CNA: GitHub_M)
October 5, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-48521 (envoyproxy envoy). Public exploit reference added.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
envoyproxy	envoy	—	< 1.36.10	—

Weaknesses

CWE-476

References (9)

https://github.com/envoyproxy/envoy/commit/8ef2da8527fcd17388b046c1add4fb47fb5d0868 [Patch]
https://github.com/envoyproxy/envoy/commit/cec4899acf03cf551f28611a5f32385648d95f96 [Patch]
https://github.com/envoyproxy/envoy/commit/e7b4839beef7f43594ce8e94c4563c80db04a8a7 [Patch]
https://github.com/envoyproxy/envoy/commit/f5436f44103fb14cb8ba42a8db0f54a06c98c45a [Patch]
https://github.com/envoyproxy/envoy/releases/tag/v1.36.10 [Release Notes]
https://github.com/envoyproxy/envoy/releases/tag/v1.37.6 [Release Notes]
https://github.com/envoyproxy/envoy/releases/tag/v1.38.4 [Release Notes]
https://github.com/envoyproxy/envoy/releases/tag/v1.39.1 [Release Notes]
https://github.com/envoyproxy/envoy/security/advisories/GHSA-5vff-j9p4-38j3 [Exploit, Vendor Advisory]

Authoritative record: CVE-2026-48521 at cve.org

Vendors: envoyproxy

Weaknesses: CWE-476

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-48521 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Thursday, October 8, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.