CVE-2021-33766

What is affected

Vendor	Microsoft
Product	Exchange Server
Weakness	CWE-287

The vulnerability

Microsoft Exchange Server contains an information disclosure vulnerability which can allow an unauthenticated attacker to steal email traffic from target.

Required action

Apply updates per vendor instructions.

US federal civilian agencies were required to act by 1 February 2022 under BOD 22-01. The deadline is a compliance date, not a measure of severity — it says nothing about how dangerous the flaw is to anyone else.

Where this comes from

Every field on this page is taken from the CISA Known Exploited Vulnerabilities catalog, last synced 11 Nov 2026, 21:30. Nothing here is our own assessment. For the technical scoring, see the NVD record below.

NVD record ↗ CVE.org record ↗