CVE-2026-73550Public exploitNetwork attack vectorHinoki check available

Proxy OOM via uncounted discarded Host headers

Published Sep 21, 2026 · Updated Sep 21, 2026

Resource exhaustion in Envoy before 1.36.10, 1.37.0 through 1.37.5, 1.38.0 through 1.38.3, and 1.39.0 allows remote attackers to cause an OOM kill. In the HTTP/2 server codec, decoded Host values are copied and then discarded when :authority exists, bypassing saveHeader byte and count accounting. Ordinary unauthenticated HTTP/2 traffic can use HPACK references to amplify those copies until the Envoy process is killed, interrupting proxied traffic.

CVSS severity7.5
High
EPSS probability0.55%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Resource exhaustion in Envoy before 1.36.10, 1.37.0 through 1.37.5, 1.38.0 through 1.38.3, and 1.39.0 allows remote attackers to cause an OOM kill. In the HTTP/2 server codec, decoded Host values are copied and then discarded when :authority exists, bypassing saveHeader byte and count accounting. Ordinary unauthenticated HTTP/2 traffic can use HPACK references to amplify those copies until the Envoy process is killed, interrupting proxied traffic.

The record

CVE
CVE-2026-73550
Published
Sep 21, 2026
Updated
Sep 21, 2026
Vendor
Envoy Proxy
Product
Envoy
Classifications
CWE-770, CWE-401, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=< 1.36.10
  2. Affected versionversion=>= 1.37.0, < 1.37.6
  3. Affected versionversion=>= 1.38.0, < 1.38.4
  4. Affected versionversion=>= 1.39.0, < 1.39.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Envoy Proxy · Envoyversion=< 1.36.10; version=>= 1.37.0, < 1.37.6; version=>= 1.38.0, < 1.38.4; version=>= 1.39.0, < 1.39.1

Published CVSS scores

7.5GitHubCVSS: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.

Activity data is delayed. The latest report is Sep 28, 2026.

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

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
CWE-401Missing Release of Memory after Effective Lifetime
T1499Endpoint Denial of Service

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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