Autobahn Python: permessage-brotli inflates a whole frame before maxMessagePayloadSize is checked (incomplete fix of GHSA-hxp9-w8x3-p566)

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-116579
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-26 21:18:15 UTC
Updated2026-10-26 21:18:15 UTC
DescriptionAutobahn 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.

Risk And Classification

Primary CVSS: v3.1 5.9 MEDIUM from [email protected]

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

Problem Types: CWE-409 | CWE-770 | CWE-409 CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) | CWE-770 CWE-770: Allocation of Resources Without Limits or Throttling

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Crossbario Autobahn-python affected >= 26.7.1, < 26.10.1 Not specified

References

ReferenceSourceLinkTags
github.com/crossbario/autobahn-python/security/advisories/GHSA-pjh6-c8mg... [email protected] github.com
github.com/crossbario/autobahn-python/releases/tag/v26_10_1 [email protected] github.com
github.com/crossbario/autobahn-python/commit/a41442bbee4f6126a8ce1bb8928... [email protected] github.com
github.com/crossbario/autobahn-python/pull/1987 [email protected] github.com
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