CVE-2026-20921
HighCVSS 7.5Exploitation Probability (EPSS)
Elevated risk64th percentile - higher than 64% of all known CVEs
Summary
A race condition in Windows SMB Server allows for concurrent execution using shared resources with improper synchronization. This enables an authorized attacker to elevate privileges over a network.
Risk Assessment
An attacker with valid credentials can exploit this vulnerability to gain higher privileges, posing a significant threat to system and data security.
Recommendation
It is recommended to update Windows SMB Server to the latest version to mitigate this vulnerability and implement additional security measures to monitor and restrict access to network resources.
Other vulnerabilities in Windows SMB Server
See all- CVE-2026-96325High
A missing reference to an active allocated resource in Windows SMB Server allows an unauthorized attacker to deny service over a network. The flaw lies in how the SMB service manages resources.
- CVE-2026-88127High
Use after free in Windows SMB Server allows an authorized attacker to elevate privileges locally.
- CVE-2026-26128High
Improper authentication in Windows SMB Server allows an authorized attacker to elevate privileges locally.
- CVE-2019-0703MediumActively exploited
An information disclosure vulnerability exists in the way that the Windows SMB Server handles certain requests, aka 'Windows SMB Information Disclosure Vulnerability'. This CVE ID is unique from CVE-2019-0704 and CVE-2019-0821.
- CVE-2026-72949High
Null pointer dereference in Windows SMB Server Network Transport Driver (srvnet.sys) allows an unauthorized attacker to deny service over a network.
- CVE-2026-69403Medium
A missing authorization vulnerability in Windows SMB Server allows an authorized attacker to disclose information locally.
- CVE-2026-69374Medium
The vulnerability in Windows SMB Server is an allocation of resources without limits or throttling. It allows an authorized attacker to deny service over a network.
- CVE-2026-62800High
Heap-based buffer overflow in Windows SMB Server allows an authorized attacker to execute code over a network.
- CVE-2026-62790High
Heap-based buffer overflow in Windows SMB Server allows an authorized attacker to execute code over a network.
- CVE-2026-57089High
Use-after-free vulnerability in Windows SMB Server Network Transport Driver (srvnet.sys) allows an unauthorized attacker to execute code over a network.
Original NVD description (English source)
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows SMB Server allows an authorized attacker to elevate privileges over a network.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS