CVE-2021-27401
CWE-79Published: August 13, 2021· Updated: Jun 17, 2026
Official Description
The Join Meeting page of Mitel MiCollab Web Client before 9.2 FP2 could allow an attacker to access (view and modify) user data by executing arbitrary code due to insufficient input validation, aka Cross-Site Scripting (XSS).
Technical Analysis
CVE-2021-27401 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation does not require any privileges, though user interaction (Required) is needed, which slightly reduces the risk of mass automated attacks.
The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.
From a weakness classification perspective (CWE-79): Cross-site scripting (XSS) vulnerabilities allow attackers to inject malicious scripts into web pages viewed by other users.
CVSS v3.1 Vector Breakdown
Affected Vendors & Products
Exploit & PoC Resources
Official Patches & Advisories
All References (4)
Quick Facts
Related CVEs (CWE-79)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-27401 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts