CVE-2026-69356: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in Microsoft Microsoft Exchange Server 2016 Cumulative Update 23

This vulnerability (CWE-79) in Microsoft Exchange Server 2016 Cumulative Update 23 arises from improper input neutralization during web page generation, enabling cross-site scripting attacks. Exploitation could allow an attacker to spoof content over a network, potentially leading to high confidentiality and integrity impacts. The CVSS 3.1 base score is 9.3 (critical), reflecting network attack vector, low attack complexity, no privileges required, user interaction required, scope changed, and high impact on confidentiality and integrity. Microsoft has published an official fix for affected versions.

Successful exploitation could allow an attacker to execute arbitrary scripts in the context of the vulnerable Exchange Server web interface, leading to spoofing attacks that compromise confidentiality and integrity of data. Availability impact is not affected. The vulnerability does not require privileges but does require user interaction. No known exploits are reported in the wild at this time.

An official fix is available from Microsoft. Administrators should apply the security update for Microsoft Exchange Server 2016 Cumulative Update 23 as detailed in the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69356. No additional mitigations are specified or required once the patch is applied.