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CVE-2021-34473

Microsoft Exchange Server Remote Code Execution

9.1 CRITICALActively exploited (CISA KEV)Used in ransomwarePublic exploitEPSS 100.0%
  1. Published14 Jul 2021
  2. Added to CISA KEV3 Nov 2021
  3. Remediation due17 Nov 2021
Actively exploited (CISA KEV)

Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution.

Added to KEV: 3 Nov 2021Federal remediation due: 17 Nov 2021Used in ransomware

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

Microsoft Exchange Server2013 · 2016 · 2019

Remediation

No fixed version is recorded in the NVD data. Check the vendor advisory for the latest guidance.

References

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Frequently asked

Is CVE-2021-34473 being actively exploited?

Yes. CVE-2021-34473 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 3 Nov 2021. It has been used in ransomware campaigns.

How severe is CVE-2021-34473?

CVE-2021-34473 has a CVSS 3.1 base score of 9.1, rated critical. EPSS estimates a 100.0% probability of exploitation.

Which products are affected by CVE-2021-34473?

Affected products include Microsoft Exchange Server.

How do I fix CVE-2021-34473?

Apply the vendor's patch or advisory guidance, then verify no affected versions remain across your devices.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2021-34473 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, Secuno flags any affected asset as top-priority automatically. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.