CVE-2021-31207
Microsoft Exchange Server Security Feature Bypass Vulnerability
What is affected
| Vendor | Microsoft |
|---|---|
| Product | Exchange Server |
| Weakness | CWE-20, CWE-434 |
The vulnerability
Microsoft Exchange Server contains an unspecified vulnerability that allows for security feature bypass.
Required action
Apply updates per vendor instructions.
US federal civilian agencies were required to act by 17 November 2021 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.
Ransomware
CISA records this vulnerability as having been used in ransomware campaigns. That is a confirmed observation, not an assessment of likelihood.
Where this comes from
Every field on this page is taken from the CISA Known Exploited Vulnerabilities catalog, last synced 12 Nov 2026, 00:29. Nothing here is our own assessment. For the technical scoring, see the NVD record below.
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