CVE-2026-116579
Autobahn Python: permessage-brotli inflates a whole frame before maxMessagePayloadSize is checked (incomplete fix of GHSA-hxp9-w8x3-p566)
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.
- Affected
- crossbario · autobahn-python
- CVSS v3.1 GITHUB
- 5.9 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H - EPSS
- 0.43% chance of exploitation in the next 30 days, 37th percentile
- Published
- 2026-10-26
- Updated
- 2026-10-27
Proof-of-concept exploits (1)
CVE references
- crossbario/autobahn-python/commit/a41442bbee4f6126a8ce1bb892840124c24d16f1REFERENCE
- crossbario/autobahn-python/pull/1987REFERENCE
- crossbario/autobahn-python/releases/tag/v26_10_1REFERENCE
- crossbario/autobahn-python/security/advisories/GHSA-pjh6-c8mg-3x7mREFERENCE