CVE-2026-47774Public exploitNetwork attack vector

Remote service termination via HTTP/2 cookie amplification

Published Jun 17, 2026 · Updated Jun 17, 2026

Denial of service in affected Envoy releases allows remote attackers to terminate the proxy via crafted HTTP/2 cookie headers. During downstream HTTP/2 processing, Envoy validates header size before merging buffered cookie fragments, while oghttp2/quiche limits encoded HPACK bytes rather than total decoded size. An unauthenticated client with downstream HTTP/2 access can use indexed references and stalled streams to retain amplified per-stream allocations until the Envoy process is OOM-terminated.

CVSS severity7.5
High
EPSS probability0.97%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in affected Envoy releases allows remote attackers to terminate the proxy via crafted HTTP/2 cookie headers. During downstream HTTP/2 processing, Envoy validates header size before merging buffered cookie fragments, while oghttp2/quiche limits encoded HPACK bytes rather than total decoded size. An unauthenticated client with downstream HTTP/2 access can use indexed references and stalled streams to retain amplified per-stream allocations until the Envoy process is OOM-terminated.

The record

CVE
CVE-2026-47774
Published
Jun 17, 2026
Updated
Jun 17, 2026
Vendor
Envoy Proxy
Product
Envoy
Classifications
CWE-405, CWE-770, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 17, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 17, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.35.11
  2. Affected versionversion=>= 1.36.0, < 1.36.7
  3. Affected versionversion=>= 1.37.0, < 1.37.3
  4. Affected versionversion=>= 1.38.0, < 1.38.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Envoy Proxy · Envoyversion=< 1.35.11; version=>= 1.36.0, < 1.36.7; version=>= 1.37.0, < 1.37.3; version=>= 1.38.0, < 1.38.1

Published CVSS scores

7.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-405Asymmetric Resource Consumption (Amplification)
CWE-770Allocation of Resources Without Limits or Throttling
T1499.003Application Exhaustion Flood

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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