Detections
Analytics

Security Updates for Microsoft Office Online Server (February 2026)

high Nessus Plugin ID 298564

Synopsis

The Microsoft Office Online Server installation on the remote host is affected by multiple vulnerabilities.

Description

The Microsoft Office Online Server installation on the remote host is missing security updates. It is, therefore, affected by the following vulnerabilities:

 - Improper input validation in Microsoft Office Excel allows an unauthorized attacker to disclose information locally. (CVE-2026-21258)

 - Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to elevate privileges locally. (CVE-2026-21259)

 - Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information locally. (CVE-2026-21261)

Solution

Microsoft has released 5002835 to address this issue.

See Also

https://support.microsoft.com/en-us/help/5002835

Plugin Details

Severity: High

ID: 298564

File Name: smb_nt_ms26_feb_office_web.nasl

Version: 1.2

Type: local

Agent: windows

Published: 2/10/2026

Updated: 2/11/2026

Supported Sensors: Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 6.7

CVSS v2

Risk Factor: High

Base Score: 7.2

Temporal Score: 5.3

Vector: CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:C

CVSS Score Source: CVE-2026-21259

CVSS v3

Risk Factor: High

Base Score: 7.8

Temporal Score: 6.8

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

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:microsoft:office_online_server, cpe:/a:microsoft:office_web_apps

Required KB Items: SMB/MS_Bulletin_Checks/Possible

Exploit Ease: No known exploits are available

Patch Publication Date: 2/10/2026

Vulnerability Publication Date: 2/10/2026

Reference Information

CVE: CVE-2026-21258, CVE-2026-21259, CVE-2026-21261

MSFT: MS26-5002835

MSKB: 5002835