CVE-2021-26421
Skype for Business and Lync Spoofing Vulnerability
6.5 Medium
Skype for Business and Lync Spoofing Vulnerability
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- Low
- User interaction
- Required
What an attacker can affect
- Confidentiality
- High
- Integrity
- Low
- Availability
- None
Exploit likelihood
1.41%Up 1.0 points since May 12, 2021
What each source reports
CVE List Score used
Skype for Business and Lync Spoofing Vulnerability
Skype for Business and Lync Spoofing Vulnerability
- Record
CVE-2021-26421- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:L/A:N/E:U/RL:O/RC:C - Updated
- 2026-11-02
EUVDEUVD-2021-13227
Skype for Business and Lync Spoofing Vulnerability
- Record
EUVD-2021-13227- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:L/A:N/E:U/RL:O/RC:C - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-w6mv-8x3w-r7w5
Skype for Business and Lync Spoofing Vulnerability
Skype for Business and Lync Spoofing Vulnerability
- Record
GHSA-w6mv-8x3w-r7w5- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:L/A:N - Updated
- 2026-11-02
NVD
Skype for Business and Lync Spoofing Vulnerability
- Record
CVE-2021-26421- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:L/A:N - CVSS 3.1
- 7.1 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N - CVSS 2.0
- 5.8 Medium
AV:N/AC:M/Au:N/C:P/I:P/A:N - Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-26421 is a medium vulnerability (CVSS 6.5) in Microsoft Lync Server, published May 11, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.41%, the 72nd percentile. No source names a fixed version.