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CVE-2026-48521— Envoy: HTTP/3 connection pool selection null-derefs in ProdClusterManagerFactory::allocateConnPool when transport_socket_options is null

Quick assessment

Affected

envoyproxy envoy

Exploitation

No confirmed in-the-wild exploitation; assess based on exposure

Recommended action

Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Envoy 是一款面向云原生应用的开源边缘及服务代理。在 1.36.10、1.37.6、1.38.4 和 1.39.1 之前的版本中，Envoy 的函数在选择不带空指针检查的情况下直接解引用以选择 HTTP/3 连接池。被合成请求（synthetic）、流量镜像（mirror）、健康检查（health-check）和异步客户端（async-client）调用所使用的实现可能不返回任何传输套接字选项。当启用和 HTTP/3 时，常规流量若到达此类上下文，可能导致 Envoy 工作进程崩溃。该问题的触发条件范围

CVSS 5.9 · Medium EPSS 0.74% · P55 Updated Sep 23, 2026

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 4

Vendor	Product	Version Range	Status
envoyproxy	envoy	`< 1.36.10`	affected
		`>= 1.37.0, < 1.37.6`	affected
		`>= 1.38.0, < 1.38.4`	affected
		`>= 1.39.0, < 1.39.1`	affected

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Vulnerability Information

Have questions about the vulnerability? See if Shenlong's analysis helps!

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Vulnerability Title

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

Source: CVE Program / CVE List V5

Vulnerability 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.

Source: CVE Program / CVE List V5

CVSS Information

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Source: CVE Program / CVE List V5

Vulnerability Type

空指针解引用

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
envoyproxy	envoy	< 1.36.10	-

II. Public POCs for CVE-2026-48521

#	POC Description	Source Link	Shenlong Link

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III. Intelligence Information for CVE-2026-48521

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Patches & Fixes for CVE-2026-48521 (4)

Other References for CVE-2026-48521 (5)

🔗 Release v1.38.4 · envoyproxy/envoy · GitHub Read full article x_refsource_MISC
🔗 Release v1.37.6 · envoyproxy/envoy · GitHub Read full article x_refsource_MISC
🔗 Release v1.39.1 · envoyproxy/envoy · GitHub Read full article x_refsource_MISC
🔗 Release v1.36.10 · envoyproxy/envoy · GitHub Read full article x_refsource_MISC
🔗 HTTP/3 connection pool selection null-derefs in ProdClusterManagerFactory::allocateConnPool when transport_socket_options is null · Advisory · envoyproxy/envoy · GitHub Read full article x_refsource_CONFIRM

https://www.cve.org/CVERecord?id=CVE-2026-48521

Same Patch Batch · envoyproxy · 2026-09-21 · 13 CVEs total

CVE-2026-73550	7.5 HIGH	Envoy: HTTP/2 Discarded Host Header 200 GB Header-Copy OOM in Envoy
CVE-2026-73512	7.5 HIGH	Envoy: use-after-free in QUIC on internal redirects
CVE-2026-73553	7.5 HIGH	Envoy: RBAC Authorization Bypass via Path Parameters
CVE-2026-73513	7.5 HIGH	Envoy: oghttp2 upstream trailers incorrect handling
CVE-2026-73548	7.5 HIGH	Envoy: Cross-user response poisoning via a generic (non-WebSocket) HTTP upgrade on Envoy's
CVE-2026-73547	7.5 HIGH	Envoy ext_authz: request `:path` pseudoheader dereferenced w/o null check
CVE-2026-73552	7.5 HIGH	Envoy: HTTP RBAC safe_regex can fail open on RFC-valid obs-text header values
CVE-2026-73546	7.4 HIGH	Envoy: Stored XSS in Admin Stats Interface (/stats?format=html)
CVE-2026-50572	5.9 MEDIUM	Envoy: ext_authz - RawHttpClientImpl onSuccess 0x0 segfault
CVE-2026-73511	5.3 MEDIUM	Envoy: Potential path-matching/authentication bypass when using Envoy in combination with
CVE-2026-73549	5.3 MEDIUM	Envoy - Incomplete fix for CVE-2026-26310: copyInternetAddressAndPort crashes on scoped IP
CVE-2026-73551	5.3 MEDIUM	Envoy: Path normalization does not handle dot and dotdot segments with parameters

IV. Related Vulnerabilities

Same product: envoy

Same vendor: envoyproxy

Same weakness: CWE-476