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High 7.5Published Jan 13, 2026
CVE-2026-20921Concurrent execution using shared resource with improper synchronization ('race condition') in Windows SMB Server allows an authorized attacker to elevate privileges over a network.
Updated under an hour ago ()
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It affects microsoft windows_10_1607 and 13 other products. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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Concurrent execution using shared resource with improper synchronization ('race condition') in Windows SMB Server allows an authorized attacker to elevate privileges over a network.
- CVSS
- 7.5 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-362
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Jul 30, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
microsoft windows_10_1607 microsoft:windows_10_1607 | before 10.0.14393.8783; before 10.0.14393.8783 | NVD |
microsoft windows_10_1809 microsoft:windows_10_1809 | before 10.0.17763.8276; before 10.0.17763.8276 | NVD |
microsoft windows_10_21h2 microsoft:windows_10_21h2 | before 10.0.19044.6809 | NVD |
microsoft windows_10_22h2 microsoft:windows_10_22h2 | before 10.0.19045.6809 | NVD |
microsoft windows_11_23h2 microsoft:windows_11_23h2 | before 10.0.22631.6491 | NVD |
microsoft windows_11_24h2 microsoft:windows_11_24h2 | before 10.0.26100.7623 | NVD |
microsoft windows_11_25h2 microsoft:windows_11_25h2 | before 10.0.26200.7623 | NVD |
microsoft windows_server_2008 microsoft:windows_server_2008 | all versions; all versions; r2 | NVD |
microsoft windows_server_2012 microsoft:windows_server_2012 | all versions; r2 | NVD |
microsoft windows_server_2016 microsoft:windows_server_2016 | before 10.0.14393.8783 | NVD |
microsoft windows_server_2019 microsoft:windows_server_2019 | before 10.0.17763.8276 | NVD |
microsoft windows_server_2022 microsoft:windows_server_2022 | before 10.0.20348.4648 | NVD |
microsoft windows_server_2022_23h2 microsoft:windows_server_2022_23h2 | before 10.0.25398.2092 | NVD |
microsoft windows_server_2025 microsoft:windows_server_2025 | before 10.0.26100.32230 | NVD |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20921vendor-advisory
- https://www.vicarius.io/vsociety/posts/cve-2026-20921-detection-script-race-condition-vulnerability-in-windows-smb-server
- https://www.vicarius.io/vsociety/posts/cve-2026-20921-remediation-script-race-condition-vulnerability-in-windows-smb-server
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.