Windows 10 Version 1607: Double Free
CVE-2026-103571 is a high-severity double free vulnerability in Windows 10 Version 1607 from Microsoft, with a CVSS 3.1 base score of 7.0 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists version 10.0.14393.9688 as the first without the flaw, so updating Windows 10 Version 1607 to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.27% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Windows 10 Version 1607 to 10.0.14393.9688 or a later version.
- Update Windows 10 Version 1809 to 10.0.17763.9487 or a later version.
- Update Windows 10 Version 21H2 to 10.0.19044.7846 or a later version.
- Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Microsoft | Windows 10 Version 1607 | 10.0.14393.0 up to, but not including, 10.0.14393.9688 | 10.0.14393.9688 |
| Microsoft | Windows 10 Version 1809 | 10.0.17763.0 up to, but not including, 10.0.17763.9487 | 10.0.17763.9487 |
| Microsoft | Windows 10 Version 21H2 | 10.0.19044.0 up to, but not including, 10.0.19044.7846 | 10.0.19044.7846 |
| Microsoft | Windows 10 Version 22H2 | 10.0.19045.0 up to, but not including, 10.0.19045.7846 | 10.0.19045.7846 |
| Microsoft | Windows 11 version 23H2 | 10.0.22631.0 up to, but not including, 10.0.22631.7711 | 10.0.22631.7711 |
| Microsoft | Windows 11 Version 24H2 | 10.0.26100.0 up to, but not including, 10.0.26100.9974 | 10.0.26100.9974 |
| Microsoft | Windows 11 Version 25H2 | 10.0.26200.0 up to, but not including, 10.0.26200.9974 | 10.0.26200.9974 |
| Microsoft | Windows 11 version 26H1 | 10.0.28000.0 up to, but not including, 10.0.28000.3501 | 10.0.28000.3501 |
| Microsoft | Windows 11 Version 26H2 | 10.0.26300.0 up to, but not including, 10.0.26300.9974 | 10.0.26300.9974 |
| Microsoft | Windows Server 2016 | 10.0.14393.0 up to, but not including, 10.0.14393.9688 | 10.0.14393.9688 |
| Microsoft | Windows Server 2016 (Server Core installation) | 10.0.14393.0 up to, but not including, 10.0.14393.9688 | 10.0.14393.9688 |
| Microsoft | Windows Server 2019 | 10.0.17763.0 up to, but not including, 10.0.17763.9487 | 10.0.17763.9487 |
| Microsoft | Windows Server 2019 (Server Core installation) | 10.0.17763.0 up to, but not including, 10.0.17763.9487 | 10.0.17763.9487 |
| Microsoft | Windows Server 2022 | 10.0.20348.0 up to, but not including, 10.0.20348.5870 | 10.0.20348.5870 |
| Microsoft | Windows Server 2025 | 10.0.26100.0 up to, but not including, 10.0.26100.33822 | 10.0.26100.33822 |
| Microsoft | Windows Server 2025 (Server Core installation) | 10.0.26100.0 up to, but not including, 10.0.26100.33822 | 10.0.26100.33822 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (microsoft.com).
Official description
An elevation of privilege vulnerability exists when the Windows Cryptography Next Generation (CNG) Key Isolation service improperly handles memory. An attacker who successfully exploited this vulnerability could run processes in an elevated context. To exploit this vulnerability, an attacker would first have to gain execution on the victim system. An attacker could then run a specially crafted application to elevate privileges. The security update addresses the vulnerability by correcting how the Windows CNG Key Isolation Service handles memory.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Double Free
The product calls free() twice on the same memory address.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- Ensure that each allocation is freed only once. After freeing a chunk, set the pointer to NULL to ensure the pointer cannot be freed again. In complicated error conditions, be sure that clean-up routines respect the state of allocation properly. If the language is object oriented, ensure that object destructors delete each chunk of memory only once.
- Use a static analysis tool to find double free instances.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
References
Recent Double Free vulnerabilities
- 9.8 Critical severity
- 7.0 High severity
- 7.5 High severity
- 7.8 High severity
- 9.8 Critical severity
- 7.8 High severity
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