CVE-2026-3298

HIGH

Out-of-bounds write in Windows asyncio.ProacterEventLoop.sock_recvfrom_into() when using nbytes

Title source: cna

Description

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.

References (6)

Core 6

Core References

Patch patch

https://github.com/python/cpython/commit/1274766d3c29007ab77245a72abbf8dce2a9db4d

View Patch ZIP pw:eip

Patch patch

https://github.com/python/cpython/pull/148809

Issue Tracking issue-tracking

https://github.com/python/cpython/issues/148808

Vendor Advisory vendor-advisory

https://mail.python.org/archives/list/[email protected]/thread/KWTPIQBOOOUNQP7UFSLBI437NJDFLA3F/

Patch patch

https://github.com/python/cpython/commit/27522b7d6e6588f03e61099dd858cd5a9314e2f2

View Patch ZIP pw:eip

Patch patch

https://github.com/python/cpython/commit/95633d2aad4721e25e4dfd9f43dfb6e1edcbd741

View Patch ZIP pw:eip

Scores

CVSS v4 8.8

EPSS 0.0037

EPSS Percentile 29.0%

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N

CISA SSVC

Vulnrichment

Exploitation none

Automatable no

Technical Impact partial

Details

CWE

CWE-787

Status published

Products (6)

Python Software Foundation/CPython 3.11.0 - 3.13.14

Python Software Foundation/CPython 3.11.0 - 3.14.5rc1

Python Software Foundation/CPython 3.11.0 - 3.15.0

Python Software Foundation/CPython 3.14.0a1 - 3.14.5rc1

Python Software Foundation/CPython 3.15.0a1 - 3.15.0

Python Software Foundation/CPython 3.15.0a1 - 3.15.0b1

Published Apr 21, 2026

Tracked Since Apr 21, 2026