Microsoft Win32K Privilege Escalation
CVE-2023-29336 is a high-severity use after free vulnerability in Windows 10 Version 1507 from Microsoft, with a CVSS 3.1 base score of 7.8 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 10.0.10240.19926 as the first without the flaw, so updating Windows 10 Version 1507 to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on May 9, 2023, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Windows 10 Version 1507 to 10.0.10240.19926 or a later version.
- Update Windows 10 Version 1607 to 10.0.14393.5921 or a later version.
- Update Windows Server 2016 to 10.0.14393.5921 or a later version.
- CISA's required action: Apply updates per vendor instructions.
- 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 1507 | 10.0.10240.0 up to, but not including, 10.0.10240.19926 | 10.0.10240.19926 |
| Microsoft | Windows 10 Version 1607 | 10.0.14393.0 up to, but not including, 10.0.14393.5921 | 10.0.14393.5921 |
| Microsoft | Windows Server 2016 | 10.0.14393.0 up to, but not including, 10.0.14393.5921 | 10.0.14393.5921 |
| Microsoft | Windows Server 2016 (Server Core installation) | 10.0.14393.0 up to, but not including, 10.0.14393.5921 | 10.0.14393.5921 |
| Microsoft | Windows Server 2008 Service Pack 2 | 6.0.6003.0 up to, but not including, 6.0.6003.22070 | 6.0.6003.22070 |
| Microsoft | Windows Server 2008 Service Pack 2 (Server Core installation) | 6.0.6003.0 up to, but not including, 6.0.6003.22070 | 6.0.6003.22070 |
| Microsoft | Windows Server 2008 R2 Service Pack 1 | 6.1.7601.0 up to, but not including, 6.1.7601.26519 | 6.1.7601.26519 |
| Microsoft | Windows Server 2008 R2 Service Pack 1 (Server Core installation) | 6.1.7601.0 up to, but not including, 6.1.7601.26519 | 6.1.7601.26519 |
| Microsoft | Windows Server 2012 | 6.2.9200.0 up to, but not including, 6.2.9200.24266 | 6.2.9200.24266 |
| Microsoft | Windows Server 2012 (Server Core installation) | 6.2.9200.0 up to, but not including, 6.2.9200.24266 | 6.2.9200.24266 |
| Microsoft | Windows Server 2012 R2 | 6.3.9600.0 up to, but not including, 6.3.9600.20969 | 6.3.9600.20969 |
| Microsoft | Windows Server 2012 R2 (Server Core installation) | 6.3.9600.0 up to, but not including, 6.3.9600.20969 | 6.3.9600.20969 |
| Microsoft | Windows 10 1507 | before 10.0.10240.19926 | 10.0.10240.19926 |
| Microsoft | Windows 10 1607 | before 10.0.14393.5921 | 10.0.14393.5921 |
| Microsoft | Windows Server 2008 | r2 | Not stated |
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
- LowNo special conditions are needed; the attack works reliably.
- 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:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (microsoft.com).
Official description
Win32k Elevation of Privilege Vulnerability
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-29336US Government Resource
Technical write-ups (may include proof of concept)
Other vulnerabilities in Windows 10 Version 1507
- 7.0 High severity
- 7.8 High severity
- 7.0 High severity
- 7.7 High severity
- 7.0 High severity
Recent Use After Free vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 8.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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