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CVE-2021-26422

23
FAUCET Score

CVE-2021-26422 is a Remote Code Execution vulnerability affecting Microsoft Skype for Business and Lync servers. With a CVSS score of 7.2 (HIGH), this vulnerability allows an authenticated attacker to execute arbitrary code remotely with high impact on confidentiality, integrity, and availability, requiring no user interaction. While not listed in CISA's KEV catalog, there is no public exploit code available (Metasploit, Nuclei, ExploitDB), and community discussion and media coverage are minimal, suggesting limited current exploitation.

Impacted Technologies

VendorProductVersion(s)CPE
2013CPE matchmatch criteria
cpe:2.3:a:microsoft:lync_server:2013:cumulative_update_10:*:*:*:*:*:*
2015CPE matchmatch criteria
cpe:2.3:a:microsoft:skype_for_business_server:2015:cumulative_update_11:*:*:*:*:*:*
2019CPE matchmatch criteria
cpe:2.3:a:microsoft:skype_for_business_server:2019:cumulative_update_5:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.2HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
1.2
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
2.22%
Probability of exploitation in next 30 days
EPSS Percentile
80.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0222 is in the 78th percentile among its peer group of 5,531 CVEs.

Social Chatter

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

Media Mentions

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

Remediation

Patch Available

Vendor Patches (4)

microsoftpatch availablevia nvd_reference
View patch
microsoftpatch availablevia msrc
Product: Microsoft Lync Server 2013 CU10Fixed in: 8308.1144
View patch
microsoftpatch availablevia msrc
Product: Skype for Business Server 2019 CU5Fixed in: 2046.369
View patch
microsoftpatch availablevia msrc
Product: Skype for Business Server 2015 CU11Fixed in: 9319.606
View patch

Vendor Advisories (1)

microsoft2021-May/CVE-2021-26422Important

Skype for Business and Lync Remote Code Execution Vulnerability

May 11, 2021

References

portal.msrc.microsoft.com / en-US/security-guidance/advisory/CVE-2021-26422
PatchVendor Advisory