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

[ Description ]Official description

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.

[ Fixes ]Fixes and patches

• autobahn 26.10.1Fixed version · GitHub Advisories · pip package autobahn: upgrade to 26.10.1 or later (affected >= 26.7.1, < 26.10.1)

[ Packages ]Affected open-source packages

• autobahn pipAffected >= 26.7.1, < 26.10.1 · fixed in 26.10.1 · GHSA-pjh6-c8mg-3x7m

[ References ]References

• github.com/crossbario/autobahn-python/commit/a41442bbee4f6126a8ce1bb892840124c24d16f1
• github.com/crossbario/autobahn-python/pull/1987
• github.com/crossbario/autobahn-python/releases/tag/v26_10_1
• github.com/crossbario/autobahn-python/security/advisories/GHSA-pjh6-c8mg-3x7m