Security Update for .NET Core (August 2021)

high Nessus Plugin ID 152488
New! Plugin Severity Now Using CVSS v3

The calculated severity for Plugins has been updated to use CVSS v3 by default. Plugins that do not have a CVSS v3 score will fall back to CVSS v2 for calculating severity. Severity display preferences can be toggled in the settings dropdown.


The remote Windows host is affected by a .NET Core denial of service (DoS) vulnerability.


The Microsoft .NET Core installation on the remote host is version 2.1.x prior to 2.1.29, 3.1.x prior to 3.1.18, or 5.x prior to 5.0.9. It is, therefore affected by a denial of service (DoS) vulnerability, as server applications providing WebSocket endpoints can be tricked into endlessly looping while trying to read a single WebSocket frame.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.


Update .NET Core, remove vulnerable packages and refer to vendor advisory.

See Also

Plugin Details

Severity: High

ID: 152488

File Name: smb_nt_ms21_aug_dotnet_core.nasl

Version: 1.4

Type: local

Agent: windows

Family: Windows

Published: 8/11/2021

Updated: 8/20/2021

Dependencies: microsoft_dotnet_core_win.nbin

Risk Information

CVSS Score Source: CVE-2021-26423


Risk Factor: Low

Score: 3.6


Risk Factor: Medium

Base Score: 5

Temporal Score: 3.7

Vector: AV:N/AC:L/Au:N/C:N/I:N/A:P

Temporal Vector: E:U/RL:OF/RC:C


Risk Factor: High

Base Score: 7.5

Temporal Score: 6.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:microsoft:.net_core

Required KB Items: installed_sw/.NET Core Windows

Exploit Ease: No known exploits are available

Patch Publication Date: 8/10/2021

Vulnerability Publication Date: 8/10/2021

Reference Information

CVE: CVE-2021-26423

IAVA: 2021-A-0379