# CVE-2026-85721: AsyncHttpClient unbounded HTTP/1.1 response decompression denial of service

Source: https://junglewise.ai/threats/cve-2026-85721-asynchttpclient-unbounded-http-1-1-response-decompression-denial  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-17. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-85721 · Severity: high · CVSS 7.5 · Published 2026-09-17

AsyncHttpClient, a popular Java library for making HTTP requests, decompresses response bodies without size limits by default. An attacker controlling or intercepting a server response can send a small compressed file that expands dramatically in memory, exhausting the client application's heap and crashing it. This impacts any application using AsyncHttpClient for external API calls or web requests.

Technologies: [AsyncHttpClient](https://junglewise.ai/threats/technologies/asynchttpclient), [org.asynchttpclient:async-http-client (Maven)](https://junglewise.ai/threats/technologies/org-asynchttpclient-async-http-client). Vendors: [AsyncHttpClient](https://junglewise.ai/threats/vendors/asynchttpclient), [Maven](https://junglewise.ai/threats/vendors/maven).

## Quick answers

**Is CVE-2026-85721 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-85721 being exploited in the wild.

**How severe is CVE-2026-85721?** High severity, with a CVSS score of 7.5, published 17 September 2026.

**Which products and versions are affected?** AsyncHttpClient 3.x up to and including 3.0.11; 2.x up to and including 2.16.0; org.asynchttpclient:async-http-client (Maven) ECOSYSTEM:introduced=3.0.0,fixed=3.0.12.

**Is there a fix for CVE-2026-85721?** Yes. org.asynchttpclient:async-http-client (Maven): upgrade to 3.0.12 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-85721 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-85721?** Check whether you run AsyncHttpClient or org.asynchttpclient:async-http-client (Maven) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- org.asynchttpclient:async-http-client (Maven): upgrade to 3.0.12 or later

  ```sh
  # set org.asynchttpclient:async-http-client to 3.0.12 in your pom.xml or build.gradle
  ```


## Technical details

The vulnerability is a decompression-bomb denial of service in AsyncHttpClient's HTTP/1.1 response decompression path. The ChannelManager.newHttpContentDecompressor() method creates Netty's HttpContentDecompressor without any cumulative size bound; Netty's maxAllocation parameter only limits individual decode steps, not the total decompressed output. A remote attacker (or a compromised/hostile server) can send a small gzip-, deflate-, snappy-, brotli-, or zstd-compressed response that decompresses to massive size across multiple chunks, causing OutOfMemoryError. The fix, available in 3.0.12 and 2.16.1, tracks accumulated decompressed bytes per response and rejects bodies exceeding a configured limit. Versions 3.0.8–3.0.10 also have an unbounded HTTP/2 decompressor.

## Affected products

- AsyncHttpClient AsyncHttpClient 3.x up to and including 3.0.11; 2.x up to and including 2.16.0

## Identifiers

- CVE-2026-85721
- GHSA-7grg-jcf7-rpmx

## Timeline

- 2026-09-17: disclosed: GHSA-7grg-jcf7-rpmx published
- 2026-09-17: patched: Fixed in AsyncHttpClient 3.0.12 (3.x line) and 2.16.1 (2.x line)

## Related threats

- [AsyncHttpClient resumable download information disclosure and file tampering](https://junglewise.ai/threats/cve-2026-102740-the-asynchttpclient-library-allows-java-applications-to-execute)
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- [AsyncHttpClient unbounded WebSocket decompression denial of service](https://junglewise.ai/threats/cve-2026-107227-asynchttpclient-unbounded-websocket-permessage-deflate)
- [AsyncHttpClient pooled connection reuse across NTLM and Negotiate logins](https://junglewise.ai/threats/cve-2026-107230-asynchttpclient-pooled-connections-can-still-be-shared-across)