How severe is CVE-2021-26422?

CVE-2021-26422 has a CVSS 3.x base score of 7.2, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-26422 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-26422?

CVE-2021-26422 primarily affects Microsoft Lync Server. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-26422?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-26422 published?

CVE-2021-26422 was published on 2021-05-11 and last updated on 2026-06-17.

CVE-2021-26422

CVE-2021-26422 is a high-severity vulnerability in Microsoft Lync Server with a CVSS 3.x base score of 7.2. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: High (CVSS 3.x base score 7.2)
CVSS v2: 6.5
EPSS exploit prediction: 2% (81st percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Microsoft Lync Server
Published: 2021-05-11
Last modified: 2026-06-17

Description

Skype for Business and Lync Remote Code Execution Vulnerability

Frequently asked questions

What is CVE-2021-26422?: Skype for Business and Lync Remote Code Execution Vulnerability
How severe is CVE-2021-26422?: CVE-2021-26422 has a CVSS 3.x base score of 7.2, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-26422 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-26422?: CVE-2021-26422 primarily affects Microsoft Lync Server. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-26422?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-26422 published?: CVE-2021-26422 was published on 2021-05-11 and last updated on 2026-06-17.

References

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26422

Affected products (3)

cpe:2.3:a:microsoft:lync_server:2013:cumulative_update_10:*:*:*:*:*:*
cpe:2.3:a:microsoft:skype_for_business_server:2015:cumulative_update_11:*:*:*:*:*:*
cpe:2.3:a:microsoft:skype_for_business_server:2019:cumulative_update_5:*:*:*:*:*:*

More vulnerabilities in Microsoft Lync Server

CVE-2013-1302 — Critical (CVSS 9.3): Microsoft Communicator 2007 R2, Lync 2010, Lync 2010 Attendee, and Lync Server 2013 do not properly handle objects in…
CVE-2022-33633 — High (CVSS 7.2): Skype for Business and Lync Remote Code Execution Vulnerability
CVE-2022-26911 — Medium (CVSS 6.5): Skype for Business Information Disclosure Vulnerability
CVE-2021-26421 — Medium (CVSS 6.5): Skype for Business and Lync Spoofing Vulnerability
CVE-2021-24099 — Medium (CVSS 6.5): Skype for Business and Lync Denial of Service Vulnerability
CVE-2021-24073 — Medium (CVSS 6.5): Skype for Business and Lync Spoofing Vulnerability

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