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.

It is, therefore, affected by a vulnerability as referenced in the ALAS2023-2026-1893 advisory.

    A denial-of-service vulnerability was found in Envoy's HTTP/2 HPACK header compression implementation. A     remote attacker could send a specially crafted HTTP/2 request that triggers disproportionately large     memory allocations on the server, leading to resource exhaustion and denial of service. (CVE-2026-47774)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The version of ecs-service-connect-agent installed on the remote host is prior to v1.34.13.2-1. It is, therefore, affected by a vulnerability as referenced in the ALAS2ECS-2026-126 advisory.

    A denial-of-service vulnerability was found in Envoy's HTTP/2 HPACK header compression implementation. A     remote attacker could send a specially crafted HTTP/2 request that triggers disproportionately large     memory allocations on the server, leading to resource exhaustion and denial of service. (CVE-2026-47774)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Type	Severity
322111	Amazon Linux 2023 : ecs-service-connect-agent (ALAS2023-2026-1893)	Nessus	Amazon Linux Local Security Checks	Local	high
322003	Amazon Linux 2 : ecs-service-connect-agent, --advisory ALAS2ECS-2026-126 (ALASECS-2026-126)	Nessus	Amazon Linux Local Security Checks	Local	high

Detections

Analytics

CVE-2026-47774

high

Tenable Plugins

high

high