Python 3.11-3.14 OOB Buffer Write in ProactorEventLoop (WS)
CVE-2026-3298 Published on April 21, 2026
Out-of-bounds write in Windows asyncio.ProacterEventLoop.sock_recvfrom_into() when using nbytes
The method "sock_recvfrom_into()" of "asyncio.ProacterEventLoop" (Windows only) was missing a boundary check for the data buffer when using nbytes parameter. This allowed for an out-of-bounds buffer write if data was larger than the buffer size. Non-Windows platforms are not affected.
Weakness Type
What is a Memory Corruption Vulnerability?
The software writes data past the end, or before the beginning, of the intended buffer. Typically, this can result in corruption of data, a crash, or code execution. The software may modify an index or perform pointer arithmetic that references a memory location that is outside of the boundaries of the buffer. A subsequent write operation then produces undefined or unexpected results.
CVE-2026-3298 has been classified to as a Memory Corruption vulnerability or weakness.
Products Associated with CVE-2026-3298
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Affected Versions
Python Software Foundation CPython:- Version 3.11.0 and below 3.15.0 is affected.