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01 Record

CVE-2021-34453

Microsoft Exchange Server Denial of Service Vulnerability

HighPUBLISHEDCNA: microsoft
CNA base score7.5 CVSS v3.xCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C

02 Description

Microsoft Exchange Server Denial of Service Vulnerability

03 Exploitation and scoring

Exploitation
Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.
SSVC decision
  • ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
  • AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
  • Technical ImpactpartialSuccessful exploitation gives limited 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
2.82% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 86.4% of scored records. A rank, not a probability.
NVD base score
7.5 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD analysis status
Modified. 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
2021-10-13 00:26Z5 YR AGO
Last updated
2024-08-04 00:12Z2 YR AGO
Reserved
2021-06-09
Assigning CNA
microsoft
Record state
PUBLISHED
Severity
High (CVSS 7.5)
CNA 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
Weaknesses
No CWE assigned
Data version
5.1
Document digest
e3f49c188a5869964059436249189ed946720bf185af1692eaf54f7f0541a675

05 Affected products

VendorProductVersionsPlatforms
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 1115.02.0 to < 15.02.0986.009x64-based Systems
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 1015.02.0 to < 15.02.0922.014x64-based Systems
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 2115.01.0 to < 15.01.2308.015x64-based Systems
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 2215.0.0 to < 15.01.2375.012x64-based Systems

06 References