Spoofing attack in Microsoft Exchange Server - CVE-2026-21527
Published: February 10, 2026 / Updated: February 19, 2026
Vulnerability identifier: #VU122555
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-21527
CWE-ID: CWE-451
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to perform spoofing attack.
The vulnerability exists due to incorrect processing of user-supplied data within the InterceptorSmtpAgent class. A remote attacker can perform spoofing attack against Exchange users.
Affected software
Microsoft Exchange Server
How to mitigate CVE-2026-21527
Install updates from vendor's website.
Microsoft Exchange Server - addressed in versions SE RTM Feb26SU 15.02.2562.037, 2016 CU23 Feb26SU 15.01.2507.066, 2019 CU14 Feb26SU 15.02.1544.039, 2019 CU15 Feb26SU 15.02.1748.043