Security Updates for Exchange (October 2021)

critical Nessus Plugin ID 154175
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 Microsoft Exchange Server installed on the remote host is affected by multiple vulnerabilities.


The Microsoft Exchange Server installed on the remote host is missing security updates. It is, therefore, affected by multiple vulnerabilities :

- A remote code execution vulnerability. An attacker can exploit this to bypass authentication and execute unauthorized arbitrary commands. (CVE-2021-26427)
- An elevation of privilege vulnerability. An attacker can exploit this to gain elevated privileges. (CVE-2021-41348)
- A session spoofing vulnerability exists. An attacker can exploit this to perform actions with the privileges of another user. (CVE-2021-41350)

- A denial of service (DoS) vulnerability. An attacker can exploit this issue to cause the affected component to deny system or application services. (CVE-2021-34453)


Microsoft has released the following security updates to address this issue:

See Also

Plugin Details

Severity: Critical

ID: 154175

File Name: smb_nt_ms21_oct_exchange.nasl

Version: 1.4

Type: local

Agent: windows

Published: 10/15/2021

Updated: 10/28/2021

Dependencies: ms_bulletin_checks_possible.nasl, microsoft_exchange_installed.nbin

Risk Information

CVSS Score Source: CVE-2021-26427


Risk Factor: High

Score: 8.1


Risk Factor: Medium

Base Score: 5.8

Temporal Score: 4.3

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

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


Risk Factor: Critical

Base Score: 9.6

Temporal Score: 8.3

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

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

Vulnerability Information

CPE: cpe:/a:microsoft:exchange_server

Required KB Items: SMB/MS_Bulletin_Checks/Possible

Exploit Ease: No known exploits are available

Patch Publication Date: 10/12/2021

Vulnerability Publication Date: 10/12/2021

Reference Information

CVE: CVE-2021-26427, CVE-2021-34453, CVE-2021-41348, CVE-2021-41350

MSKB: 5007011, 5007012

MSFT: MS21-5007011, MS21-5007012

IAVA: 2021-A-0466