CVE-2026-85721: asynchttpclient async-http-client Uncontrolled Resource Consumption

Vulnerability summary

CVE-2026-85721 is a high (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in asynchttpclient async-http-client. EPSS estimates a 0.63% chance of exploitation in the next 30 days, higher than 49.2% of scored vulnerabilities.

Timeline

1. 17-09-2026
   PublishedVulnerability first disclosed.
2. 17-09-2026
   Last modifiedVulnerability information updated.

Description

The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. From 2.0.0 until 2.16.1 and 3.0.12, automatic response decompression on the HTTP/1.1 path uses ChannelManager.newHttpContentDecompressor() to install Http1ContentDecompressor without a cumulative output-size limit. A hostile or compromised server, or an attacker who can alter a response in transit, can send a small gzip, deflate, or snappy response that expands across chunks until the client exhausts its heap and raises OutOfMemoryError; brotli and zstd are also affected when their optional codecs are present. In versions 3.0.8 through 3.0.10, the HTTP/2 decompressor is also unbounded, so switching protocols does not mitigate the issue on those releases. A limit applied to each decode call is insufficient because the response can be delivered as many small chunks, so the fixed implementation tracks total decompressed bytes for the whole response. This issue is fixed in versions 2.16.1 and 3.0.12.

• CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.
• CWE-409Improper Handling of Highly Compressed Data (Data Amplification)The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output.