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CVE-2021-24073

22
FAUCET Score

CVE-2021-24073 is a spoofing vulnerability affecting Microsoft Skype for Business and Lync servers. With a CVSS score of 7.1 (HIGH), it allows an unauthenticated attacker to achieve high confidentiality impact and low integrity impact through a low-complexity network attack requiring user interaction. While not currently listed in CISA's KEV catalog, there is no public exploit code available, nor is it actively exploited. Despite this, it has received some community attention and media coverage, indicating awareness within the cybersecurity landscape.

Impacted Technologies

VendorProductVersion(s)CPE
2013CPE matchmatch criteria
cpe:2.3:a:microsoft:lync_server:2013:*:*:*:*:*:*:*
2015CPE matchmatch criteria
cpe:2.3:a:microsoft:skype_for_business_server:2015:cu8:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
HIGH
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
1.3
Impact Score
4.7
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.62%
Probability of exploitation in next 30 days
EPSS Percentile
73.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0162 is in the 73rd percentile among its peer group of 14,875 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.2 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.1 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

microsoftpatch availablevia nvd_reference
View patch
microsoftpatch availablevia msrc
Product: Skype for Business Server 2015 CU 8
View patch
microsoftpatch availablevia msrc
Product: Microsoft Lync Server 2013
View patch

Vendor Advisories (1)

microsoft2021-Feb/CVE-2021-24073Important

Skype for Business and Lync Spoofing Vulnerability

Feb 9, 2021

References

portal.msrc.microsoft.com / en-US/security-guidance/advisory/CVE-2021-24073
PatchVendor Advisory