Microsoft Exchange Server
CVE-2021-31207 — Microsoft Exchange Server Security Feature Bypass Vulnerability
Executive Summary
None
Overview
6.6
CVSS MEDIUM
Moderate
MS Severity
Not Exploited
MS Exploit Status
Less Likely
MS Exploit Likelihood
CVSS Vector
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
ATTACK VECTOR
Network
ATTACK COMPLEXITY
High
PRIVILEGES REQUIRED
High
USER INTERACTION
None
SCOPE
Unchanged
CONFIDENTIALITY
High
INTEGRITY
High
AVAILABILITY
High
EXPLOIT CODE MATURITY
Unproven
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 5.8
EPSS Score
0.99782
probability of exploitation in the next 30 days
0.99956 percentile - updated 2026-08-14
View on FIRST.org
Affected Products
5 affected products
| Product | KB Article | Severity | Impact | Restart Required |
|---|---|---|---|---|
| Microsoft Exchange Server 2013 Cumulative Update 23 | 5003435 (Security Update) |
Moderate | Security Feature Bypass | Yes |
| Microsoft Exchange Server 2016 Cumulative Update 19 | 5003435 (Security Update) |
Moderate | Security Feature Bypass | Yes |
| Microsoft Exchange Server 2016 Cumulative Update 20 | 5003435 (Security Update) |
Moderate | Security Feature Bypass | Yes |
| Microsoft Exchange Server 2019 Cumulative Update 8 | 5003435 (Security Update) |
Moderate | Security Feature Bypass | Yes |
| Microsoft Exchange Server 2019 Cumulative Update 9 | 5003435 (Security Update) |
Moderate | Security Feature Bypass | Yes |
Patches
1 patch
| Article | Type | Restart |
|---|---|---|
5003435 |
Security Update | Yes |
Exploits & PoC
No public exploit or PoC has been linked for this CVE yet. When available, references are sourced from public repositories and may be unverified or non-functional — review carefully before use.
Detection Rules
No public Sigma or Nuclei detection rule has been mapped to this CVE yet. Coverage is concentrated on exploited / high-profile vulnerabilities; check SigmaHQ for updates.
Acknowledgments
Orange Tsai(@orange_8361) from DEVCORE Research Team working with Trend Micro Zero Day Initiative
References
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