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CVE-2026-47774— Envoy vulnerable to HTTP/2 memory exhaustion via cookie header size bypass and HPACK amplification

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.

envoyproxy Envoy是envoyproxy组织开源的一个分布式代理服务器。 envoyproxy Envoy存在资源管理错误漏洞，该漏洞源于HTTP/2下游请求处理中cookie标头字节在请求标头大小验证时未完全计算以及HPACK编码字节限制与解码后总大小限制缺失，可能导致未经身份验证的远程客户端触发过量内存消耗，造成OOM终止和拒绝服务。以下版本受到影响：1.35.11之前版本、1.36.0至1.36.7之前版本、1.37.0至1.37.3之前版本和1.38.0至1.38.1之前版本。

CVSS 7.5 · High EPSS 1.05% · P63

Affected Version Matrix 4

VendorProduct Version RangeStatus
envoyproxy envoy < 1.35.11 affected
>= 1.36.0, < 1.36.7 affected
>= 1.37.0, < 1.37.3 affected
>= 1.38.0, < 1.38.1 affected
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I. Basic Information for CVE-2026-47774

Vulnerability Information
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Vulnerability Title
Envoy vulnerable to HTTP/2 memory exhaustion via cookie header size bypass and HPACK amplification
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
不对称的资源消耗(放大攻击)
Source: CVE Program / CVE List V5
Vulnerability Title
envoyproxy Envoy 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
envoyproxy Envoy是envoyproxy组织开源的一个分布式代理服务器。 envoyproxy Envoy存在资源管理错误漏洞，该漏洞源于HTTP/2下游请求处理中cookie标头字节在请求标头大小验证时未完全计算以及HPACK编码字节限制与解码后总大小限制缺失，可能导致未经身份验证的远程客户端触发过量内存消耗，造成OOM终止和拒绝服务。以下版本受到影响：1.35.11之前版本、1.36.0至1.36.7之前版本、1.37.0至1.37.3之前版本和1.38.0至1.38.1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 < 1.35.11 -

II. Public POCs for CVE-2026-47774

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III. Intelligence Information for CVE-2026-47774

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Vendor Advisories for CVE-2026-47774 (1)

IV. Related Vulnerabilities

Same product: envoy
Same vendor: envoyproxy
Same weakness: CWE-405

V. Comments for CVE-2026-47774

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