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CVE-2024-30251: DoS in aiohttp
From: Sam Bull <9m199i () sambull org>
Date: Thu, 02 May 2024 14:48:19 +0100
Aiohttp is an HTTP client and server-side web framework in Python. This issue only affects users of the server-side web framework. We've not seen any evidence of this being exploited in the wild yet, and fixes were already included in the 3.9.4 and 3.9.5 releases. https://github.com/aio-libs/aiohttp/security/advisories/GHSA-5m98-qgg9-wh84 ### Summary An attacker can send a specially crafted POST (multipart/form-data) request. When the aiohttp server processes it, the server will enter an infinite loop and be unable to process any further requests. ### Impact An attacker can stop the application from serving requests after sending a single request. ------- For anyone needing to patch older versions of aiohttp, the minimum diff needed to resolve the issue is (located in `_read_chunk_from_length()`): diff --git a/aiohttp/multipart.py b/aiohttp/multipart.py index 227be605c..71fc2654a 100644 --- a/aiohttp/multipart.py +++ b/aiohttp/multipart.py @@ -338,6 +338,8 @@ class BodyPartReader: assert self._length is not None, "Content-Length required for chunked read" chunk_size = min(size, self._length - self._read_bytes) chunk = await self._content.read(chunk_size) + if self._content.at_eof(): + self._at_eof = True return chunk async def _read_chunk_from_stream(self, size: int) -> bytes: This does however introduce some very minor issues with handling form data. So, if possible, it would be recommended to also backport the changes in: https://github.com/aio-libs/aiohttp/commit/cebe526b9c34dc3a3da9140409db63014bc4cf19 https://github.com/aio-libs/aiohttp/commit/7eecdff163ccf029fbb1ddc9de4169d4aaeb6597 https://github.com/aio-libs/aiohttp/commit/f21c6f2ca512a026ce7f0f6c6311f62d6a638866
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- CVE-2024-30251: DoS in aiohttp Sam Bull (May 02)