Python CPython up to 3.14.x on Windows sock_recvfrom_into nbytes out-of-bounds write

CVSS Meta Temp Score
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7.0$0-$5k0.00

Summaryinfo

A vulnerability, which was classified as critical, has been found in Python CPython up to 3.14.x on Windows. This impacts the function sock_recvfrom_into. The manipulation of the argument nbytes leads to out-of-bounds write. This vulnerability is traded as CVE-2026-3298. It is possible to initiate the attack remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Python CPython up to 3.14.x on Windows. This issue affects the function sock_recvfrom_into. The manipulation of the argument nbytes with an unknown input leads to a out-of-bounds write vulnerability. Using CWE to declare the problem leads to CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-3298 since 02/26/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 310827 (Linux Distros Unpatched Vulnerability : CVE-2026-3298), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 3.15.0 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (310827) and CERT Bund (WID-SEC-2026-1222). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

  • Open Source Python

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 7.3
VulDB Meta Temp Score: 7.0

VulDB Base Score: 7.3
VulDB Temp Score: 7.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Out-of-bounds write
CWE: CWE-787 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 310827
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-3298

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: CPython 3.15.0
Patch: github.com

Timelineinfo

02/26/2026 CVE reserved
04/21/2026 +53 days Advisory disclosed
04/21/2026 +0 days VulDB entry created
04/29/2026 +8 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: 148808
Status: Confirmed

CVE: CVE-2026-3298 (🔒)
GCVE (CVE): GCVE-0-2026-3298
GCVE (VulDB): GCVE-100-358499
CERT Bund: WID-SEC-2026-1222 - CPython: Schwachstelle ermöglicht nicht spezifizierten Angriff

Entryinfo

Created: 04/21/2026 18:19
Updated: 04/29/2026 21:12
Changes: 04/21/2026 18:19 (72), 04/22/2026 12:27 (7), 04/29/2026 21:12 (2)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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