Platform
linux
Component
fuchsia-kernel
Fixed in
7d731b4e9599088ac3073956933559da7bca6a00
CVE-2021-22566 is a privilege escalation vulnerability discovered in the Fuchsia Kernel. This flaw allows attackers to bypass executability restrictions, potentially enabling user-mode processes to execute kernel-mode code. The vulnerability affects Fuchsia Kernel versions prior to 7d731b4e9599088ac3073956933559da7bca6a00. A fix has been released in version 7d731b4e9599088ac3073956933559da7bca6a00.
The core of this vulnerability lies in the incorrect handling of UXN (User eXecute Not-Allowed) and PXN (Privileged eXecute Not-Allowed) bits within the mmuflagstos1pte_attr function. Specifically, the vulnerability allows an attacker to map privileged executable pages as executable from an unprivileged context, effectively bypassing kernel-mode executability restrictions from user-mode. Conversely, it also permits mapping unprivileged executable pages as executable from a privileged context, circumventing user-mode restrictions from kernel-mode. This dual bypass significantly expands the attack surface. Successful exploitation could lead to arbitrary code execution within the kernel, granting the attacker complete control over the Fuchsia system. The ability to execute arbitrary code in kernel mode represents a severe compromise, potentially allowing for data theft, system modification, and denial of service.
This vulnerability was publicly disclosed on January 18, 2022. While no active exploitation campaigns have been definitively linked to CVE-2021-22566, the potential for privilege escalation makes it a high-value target. The vulnerability's impact on kernel-level memory protection suggests a potential inclusion in future exploit collections. It is not currently listed on the CISA KEV catalog.
Exploit Status
EPSS
0.01% (3% percentile)
CISA SSVC
The primary mitigation for CVE-2021-22566 is to upgrade the Fuchsia Kernel to version 7d731b4e9599088ac3073956933559da7bca6a00 or later. Due to the nature of the vulnerability and its impact on kernel-level memory protection, there are no readily available workarounds beyond upgrading. Consider implementing stricter access controls and privilege separation within the Fuchsia environment to limit the potential impact of a successful exploit. Regularly review and audit kernel configurations to ensure adherence to security best practices. After upgrading, verify the fix by attempting to execute a user-mode process with elevated privileges and confirming that the attempt is denied.
Update the Fuchsia kernel to a version later than commit 7d731b4e9599088ac3073956933559da7bca6a00 and rebuild the system. This will correct the incorrect UXN and PXN bit configuration, preventing unauthorized code execution in the kernel.
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CVE-2021-22566 is a vulnerability in the Fuchsia Kernel allowing user-mode processes to bypass executability restrictions and potentially execute kernel-mode code, leading to privilege escalation.
You are affected if you are running Fuchsia Kernel versions prior to 7d731b4e9599088ac3073956933559da7bca6a00. Check your system's version and upgrade if necessary.
Upgrade your Fuchsia Kernel to version 7d731b4e9599088ac3073956933559da7bca6a00 or later. This resolves the incorrect bit setting issue.
While no active exploitation campaigns have been definitively confirmed, the potential for privilege escalation makes it a high-value target and a potential future threat.
Refer to the Fuchsia security advisories for detailed information and updates regarding CVE-2021-22566: https://fuchsia.dev/security
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