CPython EUVD-2026-24136

| CVE-2026-3298 HIGH
Out-of-bounds Write (CWE-787)
2026-04-21 PSF GHSA-3p9c-22jr-wq4x
Memory Corruption Microsoft Buffer Overflow
8.8
CVSS 4.0
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CVSS VectorNVD

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

3
Re-analysis Queued
Apr 21, 2026 - 21:22 vuln.today
cvss_changed
Analysis Generated
Apr 21, 2026 - 16:30 vuln.today
CVSS changed
Apr 21, 2026 - 15:22 NVD
8.8 (HIGH)

DescriptionNVD

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.

AnalysisAI

Out-of-bounds buffer write in CPython's asyncio.ProactorEventLoop (Windows only) allows remote attackers to trigger memory corruption via oversized network data. The sock_recvfrom_into() method lacks buffer size validation when the nbytes parameter is used, enabling writes beyond allocated memory boundaries. …

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RemediationAI

Within 24 hours: identify all Python applications using asyncio.ProactorEventLoop on Windows systems via code review and runtime analysis. Within 7 days: apply CPython patch via GitHub PR #148809 to affected systems; upgrade to patched Python version for all Windows-based asyncio deployments. …

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EUVD-2026-24136 vulnerability details – vuln.today
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