Windows 10 Version 1507: Use After Free
CVE-2024-43491 is a critical-severity use after free vulnerability in Windows 10 Version 1507 from Microsoft, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 10.0.10240.20766 as the first without the flaw, so updating Windows 10 Version 1507 to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 12.9% chance of exploitation within 30 days, which is in the top 3.63% of all scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Windows 10 Version 1507 to 10.0.10240.20766 or a later version.
- Update Windows 10 1507 to 10.0.10240.20766 or a later version.
- Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Microsoft | Windows 10 Version 1507 | 10.0.10240.0 up to, but not including, 10.0.10240.20766 | 10.0.10240.20766 |
| Microsoft | Windows 10 1507 | before 10.0.10240.20766; 10.0.10240.20766 and earlier | 10.0.10240.20766 |
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
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- 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:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (microsoft.com).
Official description
Microsoft is aware of a vulnerability in Servicing Stack that has rolled back the fixes for some vulnerabilities affecting Optional Components on Windows 10, version 1507 (initial version released July 2015). This means that an attacker could exploit these previously mitigated vulnerabilities on Windows 10, version 1507 (Windows 10 Enterprise 2015 LTSB and Windows 10 IoT Enterprise 2015 LTSB) systems that have installed the Windows security update released on March 12, 2024—KB5035858 (OS Build 10240.20526) or other updates released until August 2024. All later versions of Windows 10 are not impacted by this vulnerability. This servicing stack vulnerability is addressed by installing the September 2024 Servicing stack update (SSU KB5043936) AND the September 2024 Windows security update (KB5043083), in that order. Note: Windows 10, version 1507 reached the end of support (EOS) on May 9, 2017 for devices running the Pro, Home, Enterprise, Education, and Enterprise IoT editions. Only Windows 10 Enterprise 2015 LTSB and Windows 10 IoT Enterprise 2015 LTSB editions are still under support.
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.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
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
- 8.8 High severity
- 10.0 Critical severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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