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Vulnerability · Published Apr 21, 2026 · Assigned by PSF

CVE-2026-3298Out-of-bounds write in Windows asyncio.ProacterEventLoop.sock_recvfrom_into() when using nbytes

High 8.8

In plain English

A high-severity out-of-bounds write in CPython from Python Software Foundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 34% of all known vulnerabilities).

Severity (CVSS 4.0)8.8High
Exploit odds (30 days)0.4%top 66.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Ubuntu:22.04:LTSpython3.10no fix listedUBUNTU-CVE-2026-3298
Ubuntu:24.04:LTSpython3.12no fix listedUBUNTU-CVE-2026-3298
Ubuntu:25.10python3.13no fix listedUBUNTU-CVE-2026-3298
Ubuntu:25.10python3.14no fix listedUBUNTU-CVE-2026-3298
Ubuntu:26.04:LTSpython3.14no fix listedUBUNTU-CVE-2026-3298

Affected products (as reported)

VendorProductVersions
Python Software Foundation CPython 0 – before 3.11.163.12.0 – before 3.12.143.13.0 – before 3.13.143.14.0a1 – before 3.14.5rc13.15.0a1 – before 3.15.0b1

Weakness: CWE-787 · Vector: 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

References