Deserialization of Untrusted Data in Microsoft Exchange Server - CVE-2026-55009
Published: July 16, 2026
Vulnerability identifier: #VU137889
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-55009
CWE-ID: CWE-502
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vendor: Microsoft
Affected software:
Microsoft Exchange Server
Microsoft Exchange Server
Detailed vulnerability description
The vulnerability allows a local user to escalate privileges on the target system.
The vulnerability exists due to insecure input validation when processing serialized data in Microsoft Exchange Server. A local user can pass specially crafted data to the application and gain elevated privileges on the system.
How to mitigate CVE-2026-55009
Install updates from vendor's website.