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CVE-2021-28481

63
FAUCET Score

CVE-2021-28481 is a critical Remote Code Execution (RCE) vulnerability affecting Microsoft Exchange Server. It carries a CVSS score of 9.8, indicating a severe risk due to its network-based attack vector, low attack complexity, and potential for complete compromise of confidentiality, integrity, and availability. While not listed in CISA's KEV catalog, its high EPSS score and significant community discussion suggest a high likelihood of exploitation. Although no Metasploit or ExploitDB modules exist, Nuclei templates for a related critical vulnerability (ProxyNotFound) are available, and the vulnerability received extensive media coverage upon disclosure.

Impacted Technologies

VendorProductVersion(s)CPE
2013CPE matchmatch criteria
cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*
2016CPE matchmatch criteria
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:*
2016CPE matchmatch criteria
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_20:*:*:*:*:*:*
2019CPE matchmatch criteria
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*
2019CPE matchmatch criteria
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_9:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
36.49%
Probability of exploitation in next 30 days
EPSS Percentile
98.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Nuclei: CVE-2021-28481 · Jan 20, 2026
This CVE's current EPSS score of 0.3649 is in the 96th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (6)

microsoftpatch availablevia nvd_reference
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2019 Cumulative Update 9Fixed in: 15.02.0858.010
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2016 Cumulative Update 20Fixed in: 15.01.2242.008
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2013 Cumulative Update 23Fixed in: 15.00.1497.015
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2016 Cumulative Update 19Fixed in: 15.01.2176.012
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2019 Cumulative Update 8Fixed in: 15.02.0792.013
View patch

Vendor Advisories (1)

microsoft2021-Apr/CVE-2021-28481Critical

Microsoft Exchange Server Remote Code Execution Vulnerability

Apr 13, 2021

References

portal.msrc.microsoft.com / en-US/security-guidance/advisory/CVE-2021-28481
PatchVendor Advisory