---
title: "CVE-2026-85721: AsyncHttpClient - Denial of Service"
description: "AsyncHttpClient 2.0.0 to 2.16.1 and 3.0.8 to 3.0.12 contains a denial of service caused by unbounded HTTP response decompression in Http1ContentDecompressor and HTTP/2 decompressor, letting attackers exhaust client heap memory, exploit requires attacker to send crafted compressed responses."
url: https://panop.io/threat-heartbeat/CVE-2026-85721/
---

# CVE-2026-85721 AsyncHttpClient - Denial of Service

AsyncHttpClient 2.0.0 to 2.16.1 and 3.0.8 to 3.0.12 contains a denial of service caused by unbounded HTTP response decompression in Http1ContentDecompressor and HTTP/2 decompressor, letting attackers exhaust client heap memory, exploit requires attacker to send crafted compressed responses.

CVSS base score 7.5 /10

High

CISA KEV

Not listed

Public exploit

Proof of concept available

Authentication

Not required

EPSS

0.63% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-85721)

## 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

17 September 2026

Updated

15 October 2026

Weakness

[CWE-400](https://cwe.mitre.org/data/definitions/400.html)

## Vendor fix

Update to versions 2.16.1 or 3.0.12 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-2026-85721](https://nvd.nist.gov/vuln/detail/CVE-2026-85721)
- [https://github.com/AsyncHttpClient/async-http-client/commit/e1871a19972fb496be1b8ac6be11d79e22ff2162](https://github.com/AsyncHttpClient/async-http-client/commit/e1871a19972fb496be1b8ac6be11d79e22ff2162)
- [https://github.com/AsyncHttpClient/async-http-client/commit/e9f2f7423e0f6503f529656f2955a1317e56ba14](https://github.com/AsyncHttpClient/async-http-client/commit/e9f2f7423e0f6503f529656f2955a1317e56ba14)
- [https://github.com/AsyncHttpClient/async-http-client/security/advisories/GHSA-7grg-jcf7-rpmx](https://github.com/AsyncHttpClient/async-http-client/security/advisories/GHSA-7grg-jcf7-rpmx)
- [https://github.com/AsyncHttpClient/async-http-client/commit/5ee2841cbf268bba4a200578be3938ccfc6cc6d6](https://github.com/AsyncHttpClient/async-http-client/commit/5ee2841cbf268bba4a200578be3938ccfc6cc6d6)
- [https://github.com/AsyncHttpClient/async-http-client/commit/663a1a91757904b22cfe37e2e6049f1f8ea6ae59](https://github.com/AsyncHttpClient/async-http-client/commit/663a1a91757904b22cfe37e2e6049f1f8ea6ae59)

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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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