CVE-2021-27077: Microsoft Windows win32kfull bStretch NULL Pointer Dereference Privilege Escalation Vulnerability
This vulnerability allows local attackers to escalate privileges on affected installations of Microsoft Windows. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the win32kfull.sys driver. The issue results from dereferencing a NULL pointer. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of SYSTEM.
Other sources
This vulnerability allows local attackers to escalate privileges on affected installations of Microsoft Windows. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the win32kfull.sys driver. The issue results from the lack of proper validation of a user-supplied value prior to dereferencing it as a pointer. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of SYSTEM.
— ZDI
Windows Win32k Elevation of Privilege Vulnerability
— Microsoft
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.17134.2087Patch KB5000809 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.17763.1817Patch KB5000822 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 6.3.9600.19968Patch KB5000853 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 6.1.7601.24566Patch KB5000851 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 6.2.9200.23298Patch KB5000840 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 6.0.6003.21070Patch KB5000856 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 6.3.9600.19968Patch KB5000848 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.14393.4283Patch KB5000803 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.10240.18874Patch KB5000807 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.19043.867Patch KB5000802 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.18363.1440Patch KB5000808
Event History
Frequently Asked Questions
What is the severity of CVE-2021-27077?
CVE-2021-27077 has a CVSS score indicating it allows local privilege escalation, making it a significant security threat.
How do I fix CVE-2021-27077?
To fix CVE-2021-27077, apply the relevant security patches provided by Microsoft for your affected Windows version.
Which versions of Windows are affected by CVE-2021-27077?
CVE-2021-27077 affects various versions of Microsoft Windows, including Windows 10, Windows Server, and Windows 7.
Who can exploit CVE-2021-27077?
CVE-2021-27077 can be exploited by local attackers who already have the ability to execute low-privileged code on the system.
Is there a workaround for CVE-2021-27077?
Currently, Microsoft recommends applying the security updates as the primary mitigation for CVE-2021-27077, and there are no official workarounds.