CVE-2026-20921
Windows SMB Server Elevation of Privilege Vulnerability
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows SMB Server allows an authorized attacker to elevate privileges over a network.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Windows SMB Server Elevation of Privilege Vulnerability
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows SMB Server allows an authorized attacker to elevate privileges over a network.
- Record
CVE-2026-20921- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C - Weakness
- CWE-362
- Updated
- 2026-11-02
EUVDEUVD-2026-2122
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows SMB Server allows an authorized attacker to elevate privileges over a network.
- Record
EUVD-2026-2122- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-rj95-xj64-7m2x
Concurrent execution using shared resource with improper synchronization ('race condition') in...
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows SMB Server allows an authorized attacker to elevate privileges over a network.
- Record
GHSA-rj95-xj64-7m2x- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-362
- Updated
- 2026-11-02
NVD
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows SMB Server allows an authorized attacker to elevate privileges over a network.
- Record
CVE-2026-20921- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-362
- Updated
- 2026-11-02
Affected products
- microsoft windows 10 version 1607
- microsoft windows 10 version 1809
- microsoft windows 10 version 21h2
- microsoft windows 10 version 22h2
- microsoft windows 11 version 23h2
- microsoft windows 11 version 24h2
- microsoft windows 11 version 25h2
- microsoft windows server 2008 r2 service pack 1
- microsoft windows server 2008 r2 service pack 1 (server core installation)
- microsoft windows server 2008 service pack 2
- microsoft windows server 2008 service pack 2 (server core installation)
- microsoft windows server 2012
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- microsoft windows server 2012 (server core installation)
- microsoft windows server 2012 r2
- microsoft windows server 2012 r2 (server core installation)
- microsoft windows server 2016
- microsoft windows server 2016 (server core installation)
- microsoft windows server 2019
- microsoft windows server 2019 (server core installation)
- microsoft windows server 2022
- microsoft windows server 2022, 23h2 edition (server core installation)
- microsoft windows server 2025
- microsoft windows server 2025 (server core installation)
- microsoft windows 10 1607
- microsoft windows 10 1809
- microsoft windows 10 21h2
- microsoft windows 10 22h2
- microsoft windows 11 23h2
- microsoft windows 11 24h2
- microsoft windows 11 25h2
- microsoft windows server 2008
- microsoft windows server 2022 23h2
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, published | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-20921 is a high vulnerability (CVSS 7.5) in Microsoft Windows 10 Version 1607, published January 13, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.18%, the 67th percentile. No source names a fixed version.
References
msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20921
vicarius.io/vsociety/posts/cve-2026-20921-detection-script-race-condition-vulnerability-in-windows-smb-server
nvd.nist.gov/vuln/detail/CVE-2026-20921
github.com/advisories/GHSA-rj95-xj64-7m2x