// CVE

CVE-2021-34473

Critical 9.1

Microsoft Microsoft Exchange Server 2013 Cumulative Update 23

9.1CVSS

100%EPSS

—CISA KEV

Summary

Microsoft Exchange Server Remote Code Execution Vulnerability

Published: 2021-07-14

Analysis

🟠 High — imminent exploitation

How it's exploited: Exploitable over the network (internet-reachable), unauthenticated, no user interaction, and with low complexity.

⚠️ Critical combo: remote, unauthenticated and no interaction → trivial to automate.

Impact: Confidentiality high · Integrity high · Availability none.

Status: Exploit probability (EPSS, 30 days): 100% — high.

How to defend:

Apply the vendor patch according to risk priority.
Reduce exposure: keep it off the internet; firewall, VPN or network segmentation.
Detect: turn this CVE into detection rules.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C

The vector encodes how it's exploited (translated above, in the analysis). Break it down in the CVSS tool →

🔗 NVD record 🌉 CVE → detection 🎯 Am I exposed? ⚖️ Prioritize patch

← Back to the Threat Radar

Sources: CISA KEV · EPSS · FIRST.org · NVD. Analysis derived from the CVSS vector and exploitation status (no AI). Informational; always verify against the vendor's official advisory.