Live › vulnerability › CVE-2026-116579
Go to dashboardAutobahn Python's permessage-brotli decompression runs without an output limit, so a small compressed WebSocket frame can allocate hundreds of MiB before the payload size check rejects it. An unauthenticated client can use this to cause memory-exhaustion denial of service.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-26 21:20 UTC. All times on this page are UTC.
Servers running Autobahn Python from 26.7.1 up to but not including that enable the opt-in permessage-brotli feature through the compress extra. Deflate and bzip2 compression are not part of this issue. Deployments on other versions, or without permessage-brotli enabled, can skip it.
26.10.1No product ranges from the sources yet.
pip show autobahn and check whether the installed version is between 26.7.1 and 26.10.1.compress extra is installed and the permessage-brotli feature is enabled in the WebSocket server configuration (unknown if the sources give the exact setting name).26.10.1 or later.Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
Autobahn Python is a WebSocket and WAMP implementation for Python that supports Twisted and asyncio. From 26.7.1 until 26.10.1, PerMessageBrotli.decompress_message_data in compress_brotli.py calls the Brotli decompressor without an output limit and checks maxMessagePayloadSize only after a complete frame has been inflated. An unauthenticated WebSocket client can send a small, highly compressed frame that allocates hundreds of MiB before rejection, causing memory-exhaustion denial of service on servers that enable the opt-in permessage-brotli feature through the compress extra. Deflate and bzip2 already enforce the remaining output budget and are outside this residual vulnerability. This issue is fixed in version 26.10.1.
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