CVE-2026-73549Network attack vectorHinoki check available

Authenticated proxy crash via scoped IPv6 reconstruction

Published Sep 21, 2026 · Updated Sep 21, 2026

Denial of service in affected Envoy releases allows remote authenticated users to crash the proxy via scoped IPv6 addresses. Utility::copyInternetAddressAndPort and two QUIC client-address paths stringify a scoped IPv6 address with its percent scope identifier, then pass that string to Ipv6Instance even though inet_pton cannot parse the suffix. Reachability requires a kernel-provided scoped IPv6 original destination in a transparent-proxy ORIGINAL_DST deployment or an affected QUIC client path; the HTTP header override rejects such addresses earlier.

CVSS severity5.3
Medium
EPSS probability0.62%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Denial of service in affected Envoy releases allows remote authenticated users to crash the proxy via scoped IPv6 addresses. Utility::copyInternetAddressAndPort and two QUIC client-address paths stringify a scoped IPv6 address with its percent scope identifier, then pass that string to Ipv6Instance even though inet_pton cannot parse the suffix. Reachability requires a kernel-provided scoped IPv6 original destination in a transparent-proxy ORIGINAL_DST deployment or an affected QUIC client path; the HTTP header override rejects such addresses earlier.

The record

CVE
CVE-2026-73549
Published
Sep 21, 2026
Updated
Sep 21, 2026
Vendor
Envoy Proxy
Product
Envoy
Classifications
CWE-754, T1499.004
Attack vector
network
Privileges
authenticated

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

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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=< 1.36.10
  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 privilegesauthenticated

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

5.3GitHub Security AdvisoryCVSS:3.1/AV:N/AC:H/PR:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-754Improper Check for Unusual or Exceptional Conditions
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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