---
title: "CVE-2026-73550: Envoy - Denial of Service"
description: "Envoy < 1.36.10, 1.37.6, 1.38.4, and 1.39.1 contains a denial of service caused by improper handling of HTTP/2 Host header values and HPACK indexing, letting unauthenticated clients exhaust memory, exploit requires HTTP/2 HPACK and duplicate Host discard behavior."
url: https://panop.io/threat-heartbeat/CVE-2026-73550/
---

# CVE-2026-73550 Envoy - Denial of Service

Envoy < 1.36.10, 1.37.6, 1.38.4, and 1.39.1 contains a denial of service caused by improper handling of HTTP/2 Host header values and HPACK indexing, letting unauthenticated clients exhaust memory, exploit requires HTTP/2 HPACK and duplicate Host discard behavior.

CVSS base score 7.5 /10

High

CISA KEV

Not listed

Public exploit

Proof of concept available

Authentication

Not required

EPSS

0.55% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-73550)

## Details

Type

Denial of Service

Impact

Denial Of Service

CVSS vector

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

Published

21 September 2026

Updated

15 October 2026

Weakness

[CWE-401](https://cwe.mitre.org/data/definitions/401.html)

## Vendor fix

Update to versions 1.36.10, 1.37.6, 1.38.4, or 1.39.1 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-73550](https://nvd.nist.gov/vuln/detail/CVE-2026-73550)
- [https://github.com/envoyproxy/envoy/releases/tag/v1.37.6](https://github.com/envoyproxy/envoy/releases/tag/v1.37.6)
- [https://github.com/envoyproxy/envoy/releases/tag/v1.39.1](https://github.com/envoyproxy/envoy/releases/tag/v1.39.1)
- [https://github.com/envoyproxy/envoy/commit/0910997f70e91d2d20c329bb507bfce44ce01f80](https://github.com/envoyproxy/envoy/commit/0910997f70e91d2d20c329bb507bfce44ce01f80)
- [https://github.com/envoyproxy/envoy/commit/1fec994c868df008cdd4ae285aab58a196fd31f2](https://github.com/envoyproxy/envoy/commit/1fec994c868df008cdd4ae285aab58a196fd31f2)
- [https://github.com/envoyproxy/envoy/commit/fc75d8e35b0d11acbae18b63a0bd96e32e84f61b](https://github.com/envoyproxy/envoy/commit/fc75d8e35b0d11acbae18b63a0bd96e32e84f61b)
- [https://github.com/envoyproxy/envoy/releases/tag/v1.36.10](https://github.com/envoyproxy/envoy/releases/tag/v1.36.10)
- [https://github.com/envoyproxy/envoy/releases/tag/v1.38.4](https://github.com/envoyproxy/envoy/releases/tag/v1.38.4)
- [https://github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvh](https://github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvh)
- [https://github.com/envoyproxy/envoy/commit/3fd0ffee7ac87adf3bc6e421656bb96310512300](https://github.com/envoyproxy/envoy/commit/3fd0ffee7ac87adf3bc6e421656bb96310512300)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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