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CVE-2026-85721— AsyncHttpClient: Unbounded HTTP/1.1 response decompression enables a decompression-bomb denial of service

Quick assessment

Affected
AsyncHttpClient async-http-client
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

AsyncHttpClient (AHC) 库使 Java 应用程序能够轻松执行 HTTP 请求并异步处理 HTTP 响应。在 2.0.0 至 2.16.1 以及 3.0.12 之前的版本中，HTTP/1.1 路径上的自动响应解压缩功能通过 安装 ，但未对累计输出大小设置限制。恶意服务器或已受感染的服务器，以及能够在传输过程中篡改响应的攻击者，可以发送一个较小的 gzip、deflate 或 snappy 压缩响应，该响应在分块传输过程中不断解压扩展，直至耗尽客户端堆内存并触发 。如果系统中存在可选的编解码器，br

CVSS 7.5 · High
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I. Basic Information for CVE-2026-85721

Vulnerability Information
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Vulnerability Title
AsyncHttpClient: Unbounded HTTP/1.1 response decompression enables a decompression-bomb denial of service
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
AsyncHttpClient async-http-client >= 2.0.0, < 2.16.1 -

II. Public POCs for CVE-2026-85721

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III. Intelligence Information for CVE-2026-85721

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Patches & Fixes for CVE-2026-85721 (3)

Vendor Advisories for CVE-2026-85721 (1)

Same Patch Batch · AsyncHttpClient · 2026-09-17 · 6 CVEs total

CVE-2026-85719 7.5 HIGH AsyncHttpClient: SOCKS proxy credentials sent to the origin server over plaintext HTTP
CVE-2026-85717 6.8 MEDIUM AsyncHttpClient: Client-wide realm credentials re-sent to a cross-origin redirect target
CVE-2026-85718 5.9 MEDIUM AsyncHttpClient: Connection permit leak on TLS handshake failure causes per-host denial of
CVE-2026-85720 5.9 MEDIUM AsyncHttpClient: Origin credentials sent to the proxy on the plaintext CONNECT request
CVE-2026-85716 3.7 LOW AsyncHttpClient: SCRAM and Digest mutual-authentication responses are not verified

IV. Related Vulnerabilities

Same product: async-http-client
Same vendor: AsyncHttpClient
Same weakness: CWE-400

V. Comments for CVE-2026-85721

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