Bug 2561109 (CVE-2026-116579)

Summary:	CVE-2026-116579 autobahn: autobahn: Denial of Service via uncontrolled Brotli decompression
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	dschmidt, eglynn, jjoyce, jlanda, jpretori, jschluet, jwong, kshier, lhh, mburns, mgarciac, omaciel, rbobbitt, simaishi, stcannon, yguenane
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in autobahn. An unauthenticated remote attacker can exploit this vulnerability by sending a small, highly compressed WebSocket message to a server configured with Brotli compression. Because decompression occurs without enforcing an output size limit during processing, the payload can consume excessive memory before being rejected, resulting in a Denial of Service (DoS).	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
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Description OSIDB Bzimport 2026-10-26 20:56:38 UTC

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.