CVE-2026-3298 PUBLISHED

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.

• GGAutomaton (https://github.com/GGAutomaton) reporter
• Victor Stinner (https://github.com/vstinner) remediation reviewer
• Seth Larson (https://github.com/sethmlarson) coordinator

• https://github.com/python/cpython/pull/148809
• https://github.com/python/cpython/issues/148808
• https://mail.python.org/archives/list/security-announce@python.org/thread/KWTPIQBOOOUNQP7UFSLBI437NJDFLA3F/
• https://github.com/python/cpython/commit/1274766d3c29007ab77245a72abbf8dce2a9db4d
• https://github.com/python/cpython/commit/27522b7d6e6588f03e61099dd858cd5a9314e2f2
• https://github.com/python/cpython/commit/95633d2aad4721e25e4dfd9f43dfb6e1edcbd741

• CWE-787 Out-of-bounds write CWE