AsyncHttpClient: Unbounded WebSocket permessage-deflate decompression enables a decompression-bomb denial of service when compression is enabled

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The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. From 2.2.0 until 3.0.14, WebSocket permessage-deflate decompression is unbounded when compression is enabled. The inbound pipeline aggregates compressed frames before WebSocketClientCompressionHandler inflates them, so webSocketMaxFrameSize and webSocketMaxBufferSize do not bound decompressed output. A malicious WebSocket peer can send a small compressed message that expands to a very large Netty buffer and exhausts JVM heap. This issue is fixed in version 3.0.14.

Source published

7 Oct 2026 20:51:04 UTC

Source modified

8 Oct 2026 14:02:28 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H