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CVE-2026-47221— Envoy: Null pointer deref in internal redirects

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 Proxy Envoy是Envoy Proxy团队的应用网关。 Envoy Proxy Envoy存在异常处理不当漏洞，该漏洞源于路由过滤器中的空指针取消引用，可能导致未经身份验证的攻击者通过HTTP 303内部重定向，造成拒绝服务，中断所有活动连接。以下版本受到影响：1.35.13版本之前版本、1.36.9版本之前版本、1.37.5版本之前版本和1.38.3版本之前版本。

CVSS 5.9 · Medium EPSS 0.45% · P36

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 4

VendorProduct Version RangeStatus
envoyproxy envoy >= 1.38.0, < 1.38.3 affected
>= 1.37.0, < 1.37.5 affected
>= 1.36.0, < 1.36.9 affected
>= 1.18.0, < 1.35.13 affected
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I. Basic Information for CVE-2026-47221

Vulnerability Information
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Vulnerability Title
Envoy: Null pointer deref in internal redirects
Source: CVE Program / CVE List V5
Vulnerability Description
Envoy is an open source edge and service proxy designed for cloud-native applications. From 1.18.0 until 1.35.13, 1.36.9, 1.37.5, and 1.38.3, the router filter contains a null pointer dereference vulnerability when handling HTTP 303 (See Other) internal redirects for body-less non-GET/HEAD requests. When a POST, PUT, DELETE, or PATCH request without a body is sent to a route configured with internal redirect policy that includes 303 in redirect_response_codes, and the upstream responds with HTTP 303, the redirect handling code attempts to drain a request body buffer that was never allocated. This results in a segmentation fault that crashes the entire Envoy process. When route configured with internal_redirect_policy including 303 in redirect_response_codes and upstream must return HTTP 303 response, an unauthenticated attacker can exploit this to cause complete denial of service, terminating all active connections. This vulnerability is fixed in 1.35.13, 1.36.9, 1.37.5, and 1.38.3.
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
Vulnerability Title
Envoy Proxy Envoy 异常处理不当漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Envoy Proxy Envoy是Envoy Proxy团队的应用网关。 Envoy Proxy Envoy存在异常处理不当漏洞，该漏洞源于路由过滤器中的空指针取消引用，可能导致未经身份验证的攻击者通过HTTP 303内部重定向，造成拒绝服务，中断所有活动连接。以下版本受到影响：1.35.13版本之前版本、1.36.9版本之前版本、1.37.5版本之前版本和1.38.3版本之前版本。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
envoyproxy envoy >= 1.38.0, < 1.38.3 -

II. Public POCs for CVE-2026-47221

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III. Intelligence Information for CVE-2026-47221

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Vendor Advisories for CVE-2026-47221 (1)

Same Patch Batch · envoyproxy · 2026-06-26 · 14 CVEs total

CVE-2026-48743 7.5 HIGH Envoy: HTTP/3 to HTTP/1 request smuggling via headers-only request with nonzero Content-Le
CVE-2026-48042 7.5 HIGH Envoy: Stack overflow in destructor of highly nested JSON
CVE-2026-48044 7.5 HIGH Envoy Zstd Decompressor: Ratio Check at Wrong Loop Depth lead to memory explosion
CVE-2026-47220 7.5 HIGH Envoy: Segmentation fault when using %REQUESTED_SERVER_NAME% in log format
CVE-2026-47775 6.8 MEDIUM Envoy OAuth2 Filter: Padding Oracle via AES-256-CBC Cookie Decryption
CVE-2026-47204 6.5 MEDIUM Envoy: grpc_stats filter segfault on Connect protocol requests to direct_response routes
CVE-2026-47207 6.5 MEDIUM Envoy crashes if multiple unexpected ext_proc responses are packed into one gRPC message
CVE-2026-48497 5.9 MEDIUM Envoy: Abnormal process termination in DNS UDP filter
CVE-2026-48706 5.9 MEDIUM Envoy Heap Buffer Overflow in TcpStatsdSink
CVE-2026-47205 5.9 MEDIUM Envoy: ext_authz Use-After-Free during Stream Teardown with Per-Route Overrides
CVE-2026-48090 5.9 MEDIUM Envoy HTTP: OAuth2 filter late async token completion after stream teardown (UAF / crash r
CVE-2026-47692 4.8 MEDIUM Envoy: PROXY Protocol v2 header generator emits "skipped" TLVs, causing 65 KB attacker-con
CVE-2026-47778 4.4 MEDIUM Envoy: Embedded NUL in TLS DNS SAN Truncation in the Default TLS Certificate Validator. (A

IV. Related Vulnerabilities

Same product: envoy
Same vendor: envoyproxy
Same weakness: CWE-476

V. Comments for CVE-2026-47221

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