CVE-2021-31979Exploited in the wildNVD status: Analyzed
Microsoft Windows Kernel Privilege Escalation
CVE-2021-31979 is a high-severity improper restriction of operations within the bounds of a memory buffer 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 10.0.10240.19003 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 November 3, 2021, which means attacks have been observed in the wild.
Patch now
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Windows 10 Version 1507 to 10.0.10240.19003 or a later version.
- Update Windows 10 Version 1607 to 10.0.14393.4530 or a later version.
- Update Windows 10 Version 1809 to 10.0.17763.2061 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, 10.0.10240.19003 | 10.0.10240.19003 |
| Microsoft | Windows 10 Version 1607 | 10.0.14393.0 up to, but not including, 10.0.14393.4530 | 10.0.14393.4530 |
| Microsoft | Windows 10 Version 1809 | 10.0.17763.0 up to, but not including, 10.0.17763.2061; 10.0.0 up to, but not including, 10.0.17763.2061 | 10.0.17763.2061 |
| Microsoft | Windows 10 Version 1909 | 10.0.0 up to, but not including, 10.0.18363.1679 | 10.0.18363.1679 |
| Microsoft | Windows 10 Version 2004 | 10.0.0 up to, but not including, 10.0.19041.1110 | 10.0.19041.1110 |
| Microsoft | Windows 10 Version 20H2 | 10.0.0 up to, but not including, 10.0.19042.1110 | 10.0.19042.1110 |
| Microsoft | Windows 10 Version 21H1 | 10.0.0 up to, but not including, 10.0.19043.1110 | 10.0.19043.1110 |
| Microsoft | Windows 7 | 6.1.0 up to, but not including, 6.1.7601.25661 | 6.1.7601.25661 |
| Microsoft | Windows 7 Service Pack 1 | 6.1.0 up to, but not including, 6.1.7601.25661 | 6.1.7601.25661 |
| Microsoft | Windows 8.1 | 6.3.0 up to, but not including, 6.3.9600.20069 | 6.3.9600.20069 |
| Microsoft | Windows Server 2008 R2 Service Pack 1 | 6.1.7601.0 up to, but not including, 6.1.7601.25661 | 6.1.7601.25661 |
| Microsoft | Windows Server 2008 R2 Service Pack 1 (Server Core installation) | 6.1.7601.0 up to, but not including, 6.1.7601.25661 | 6.1.7601.25661 |
| Microsoft | Windows Server 2008 Service Pack 2 | 6.0.6003.0 up to, but not including, 6.0.6003.21167 | 6.0.6003.21167 |
| Microsoft | Windows Server 2008 Service Pack 2 (Server Core installation) | 6.0.6003.0 up to, but not including, 6.0.6003.21167 | 6.0.6003.21167 |
| Microsoft | Windows Server 2012 | 6.2.9200.0 up to, but not including, 6.2.9200.23409 | 6.2.9200.23409 |
| Microsoft | Windows Server 2012 (Server Core installation) | 6.2.9200.0 up to, but not including, 6.2.9200.23409 | 6.2.9200.23409 |
| Microsoft | Windows Server 2012 R2 | 6.3.9600.0 up to, but not including, 6.3.9600.20069 | 6.3.9600.20069 |
| Microsoft | Windows Server 2012 R2 (Server Core installation) | 6.3.9600.0 up to, but not including, 6.3.9600.20069 | 6.3.9600.20069 |
| Microsoft | Windows Server 2016 | 10.0.14393.0 up to, but not including, 10.0.14393.4530 | 10.0.14393.4530 |
| Microsoft | Windows Server 2016 (Server Core installation) | 10.0.14393.0 up to, but not including, 10.0.14393.4530 | 10.0.14393.4530 |
| Microsoft | Windows Server 2019 | 10.0.17763.0 up to, but not including, 10.0.17763.2061 | 10.0.17763.2061 |
| Microsoft | Windows Server 2019 (Server Core installation) | 10.0.17763.0 up to, but not including, 10.0.17763.2061 | 10.0.17763.2061 |
| Microsoft | Windows Server version 2004 | 10.0.0 up to, but not including, 10.0.19041.1110 | 10.0.19041.1110 |
| Microsoft | Windows Server version 20H2 | 10.0.0 up to, but not including, 10.0.19042.1110 | 10.0.19042.1110 |
| Microsoft | Windows 10 1507 | before 10.0.10240.19003 | 10.0.10240.19003 |
Version data comes from the organisation that assigned the CVE; 10 further products are omitted here. 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 NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA (microsoft.com) |
| CVSS 3.1 | 7.8 | High | NVD |
| CVSS 3.1 | 7.8 | High | CISA (ADP) |
| CVSS 2.0 | 7.2 | High | NVD |
Official description
Windows Kernel Elevation of Privilege Vulnerability
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Restriction of Operations within the Bounds of a Memory Buffer
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary.
How developers prevent this class of flaw
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
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
Advisories
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31979US Government Resource
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 Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerabilities
- 8.8 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 10.0 Critical severity
Microsoft SMBv3 Remote Code Execution Exploited
- 7.8 High severity
- 7.8 High severity
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