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Miggo AIRoot Cause AnalysisThe vulnerability is a form of data amplification (zip bomb) caused by the way aiohttp's StreamReader handles compressed data streams. The core of the issue lies in the _read_nowait method. When instructed to read the entire buffer (n=-1), its previous implementation could get caught in a loop. Reading from the stream would trigger decompression, which could add more data to the very buffer being read. The while loop would then process this newly added data in the same operation, leading to a single, massive memory allocation when all the decompressed chunks were joined together.
The patch addresses this by modifying _read_nowait to first record the number of chunks currently in the buffer and then read only that specific number of chunks. This prevents the function from processing data that is added re-entrantly during the read operation, thus bounding the memory usage per read.
The public-facing functions StreamReader.readany and StreamReader.read_nowait are the primary ways developers would interact with the stream and trigger the vulnerable behavior in _read_nowait. Therefore, any runtime profile of an exploit would likely show calls to these functions leading to the problematic allocation within _read_nowait.
StreamReader._read_nowaitaiohttp/streams.py
StreamReader.readanyaiohttp/streams.py
StreamReader.read_nowaitaiohttp/streams.py
| Package Name | Ecosystem | Vulnerable Versions | First Patched Version |
|---|---|---|---|
| aiohttp | pip | <= 3.14.0 | 3.14.1 |