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01 Record

CVE-2021-31207

Microsoft Exchange Server Security Feature Bypass Vulnerability

MediumKEVPUBLISHEDCNA: microsoft
CNA base score6.6 CVSS v3.xCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
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02 Description

Microsoft Exchange Server Security Feature Bypass Vulnerability

03 Exploitation and scoring

Exploitation
Exploited in the wild. Listed in the CISA Known Exploited Vulnerabilities catalog on 2021-11-03. Federal remediation due 2021-11-17. Known ransomware campaign use: reported by CISA.
SSVC decision
  • ExploitationactiveCISA reports credible evidence of active exploitation.
  • AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
  • Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
99.78% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 99.9% of scored records. A rank, not a probability.
NVD base score
6.6 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
NVD analysis status
Analyzed. NVD last modified this record on 2026-06-17.
Red Hat severity
No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2021-05-11 19:11Z5 YR AGO
Last updated
2025-10-21 23:25Z1 YR AGO
Reserved
2021-04-14
Assigning CNA
microsoft
Record state
PUBLISHED
Severity
Medium (CVSS 6.6)
CNA 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
Weaknesses
  • CWE-434Unrestricted Upload of File with Dangerous TypeBase
Data version
5.1
Document digest
2c005e4d0e8a971d94896c0f52756ba484042cd08f39754ad91f8dff0b419a57

05 Affected products

VendorProductVersionsPlatforms
MicrosoftMicrosoft Exchange Server 2013 Cumulative Update 2315.00.0 to < 15.00.1497.018x64-based Systems
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 915.02.0 to < 15.02.0858.012x64-based Systems
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 2015.01.0 to < 15.01.2242.010x64-based Systems
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 1915.01.0 to < 15.01.2176.014x64-based Systems
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 815.02.0 to < 15.02.0792.015x64-based Systems

06 References