Microsoft Exchange Server
CVE-2021-34453 — Microsoft Exchange Server Denial of Service Vulnerability
Executive Summary
None
Overview
7.5
CVSS HIGH
Important
MS Severity
Not Exploited
MS Exploit Status
Less Likely
MS Exploit Likelihood
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C
ATTACK VECTOR
Network
ATTACK COMPLEXITY
Low
PRIVILEGES REQUIRED
None
USER INTERACTION
None
SCOPE
Unchanged
CONFIDENTIALITY
None
INTEGRITY
None
AVAILABILITY
High
EXPLOIT CODE MATURITY
Unproven
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 6.5
EPSS Score
0.02674
probability of exploitation in the next 30 days
0.83824 percentile - updated 2026-06-21
View on FIRST.org
Affected Products
4 affected products
| Product | KB Article | Severity | Impact | Restart Required |
|---|---|---|---|---|
| Microsoft Exchange Server 2016 Cumulative Update 21 | 5007012 (Security Update) |
Important | Denial of Service | Yes |
| Microsoft Exchange Server 2016 Cumulative Update 22 | 5007012 (Security Update) |
Important | Denial of Service | Yes |
| Microsoft Exchange Server 2019 Cumulative Update 10 | 5007012 (Security Update) |
Important | Denial of Service | Yes |
| Microsoft Exchange Server 2019 Cumulative Update 11 | 5007012 (Security Update) |
Important | Denial of Service | Yes |
Patches
1 patch
| Article | Type | Restart |
|---|---|---|
5007012 |
Security Update | Yes |
Known Exploits
No known exploits have been linked for this CVE yet. When available, exploit references will be sourced from public repositories and may be unverified, incomplete, or non-functional. Always review code carefully before use in any environment.
Acknowledgments
References
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