Improper validation of integrity check value in Microsoft Exchange Server - CVE-2021-31209

Vulnerability identifier: #VU53082

CSH Severity: Medium

CVSS v4.0: CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green

CVE-ID: CVE-2021-31209

CWE-ID: CWE-354

Exploitation vector: Adjecent network

Exploit availability: No public exploit available

Vendor: Microsoft

Affected software:
Microsoft Exchange Server

The vulnerability allows a remote attacker to bypass integrity checks.

The vulnerability exists within the handling of Exchange Server Help updates. A remote attacker on the local network can bypass integrity check on update downloads.

Install updates from vendor's website.

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31209
• https://www.zerodayinitiative.com/advisories/ZDI-21-615/