What is the CVSS score of CVE-2026-47774?

CVE-2026-47774 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. EPSS exploitation probability: 0.6%.

Which versions of Envoy Proxy are affected by CVE-2026-47774?

Envoy proxy versions prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1 contain a high-severity denial-of-service vulnerability that allows unauthenticated remote clients to crash the proxy through memory…. A patch is available.

How to fix or mitigate CVE-2026-47774?

Within 24 hours: Inventory all Envoy instances and versions; configure HTTP/2 request logging and establish baseline memory metrics. Within 7 days: Deploy compensating controls listed below and establish maintenance windows for patching. Within 30 days: Upgrade all affected instances to patched versions 1.35.11, 1.36.7, 1.37.3, or 1.38.1 (select based on your release stream).

Envoy Proxy CVE-2026-47774

HIGH

Asymmetric Resource Consumption (Amplification) (CWE-405)

2026-06-17 GitHub_M

Denial Of Service Envoy

7.5

CVSS 3.1 · Vendor: GitHub_M

Severity by source

Vendor (GitHub_M) PRIMARY

7.5 HIGH

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

vuln.today AI

7.5 HIGH

Network-reachable HTTP/2 listener, no auth or user interaction, low complexity to send crafted HPACK headers; impact limited to availability via OOM, with no confidentiality or integrity effect.

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

4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Red Hat

7.5 HIGH

qualitative

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Lifecycle Timeline

Analysis Generated

Jun 17, 2026 - 18:03 vuln.today

DescriptionCVE.org

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.

AnalysisAI

Denial of service in Envoy versions prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1 allows unauthenticated remote clients to trigger excessive memory consumption via crafted HTTP/2 requests, potentially causing OOM termination of the Envoy process. The flaw stems from cookie header bytes bypassing request header size validation combined with HPACK limits being enforced only on encoded bytes. No public exploit identified at time of analysis, but the network-reachable, no-auth attack profile makes it a credible availability threat for edge proxies.

Technical ContextAI

Envoy is a widely deployed L7 edge/service proxy used in service meshes (Istio, Consul) and ingress gateways. The vulnerability sits in Envoy's downstream HTTP/2 request processing path, specifically the interaction between Envoy's request header size accounting and the oghttp2/quiche HPACK decoder. HPACK (RFC 7541) compresses HTTP/2 headers, and the bug is twofold: Envoy excludes cookie header bytes from its header-size validation, and oghttp2/quiche enforces block limits on the wire-encoded (compressed) size rather than the decoded size. CWE-405 (Asymmetric Resource Consumption / Amplification) accurately captures the root cause - small compressed input yields large decoded allocations. Affected CPE is cpe:2.3:a:envoyproxy:envoy across all versions before the listed fix releases.

RemediationAI

Vendor-released patch: upgrade to Envoy 1.35.11, 1.36.7, 1.37.3, or 1.38.1 depending on your maintenance branch, as published in advisory GHSA-22m2-hvr2-xqc8 (https://github.com/envoyproxy/envoy/security/advisories/GHSA-22m2-hvr2-xqc8). The vendor states no complete workaround is known short of patching. Temporary mitigations called out by the project include disabling downstream HTTP/2 where operationally feasible (trade-off: loss of HTTP/2 multiplexing, higher latency, and broken clients that require HTTP/2 such as gRPC-web), enforcing stricter request header and cookie size limits at an upstream device or CDN before traffic reaches Envoy (trade-off: may break apps with large legitimate cookies/session tokens), and monitoring Envoy memory usage for abnormal growth under HTTP/2 traffic so OOM events can be correlated and rate-limited or auto-restarted.