Buggy SELinux Lockdown Permission Checks in Kernel
Summary
UVI-2021-1000799: bpf, lockdown, audit: Fix buggy SELinux lockdown permission checks. Affects Kernel versions >= 59438b46471ae6cdfb761afc8c9beaf1e428a331, < acc43fc6cf0d50612193813c5906a1ab9d433e1e. No fix is published. How to fix ↓
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Background
The Kernel is a critical component of the Linux operating system that provides core functionalities and acts as an interface between hardware and software. It manages system resources, facilitates communication between processes, and enforces security policies. SELinux (Security-Enhanced Linux) is a security module within the Kernel that implements mandatory access control policies to protect the system from unauthorized access and privilege escalation. However, a vulnerability has been discovered in the SELinux lockdown permission checks, which could potentially be exploited by attackers to bypass security restrictions.
Vulnerability Detail
The vulnerability arises from buggy SELinux lockdown permission checks in the Kernel. These checks are intended to enforce lockdown restrictions on the use of BPF (Berkeley Packet Filter) programs, which are used for network packet filtering and analysis. However, due to the bug, the permission checks are not properly validating the lockdown status, allowing unauthorized access to BPF programs. This could lead to various security issues, such as privilege escalation, unauthorized network access, and information disclosure. The vulnerability was introduced in Kernel version v5.6 and has been fixed in version v5.12.10.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
As a temporary workaround, users can disable SELinux lockdown by modifying the system configuration. However, this should only be considered as a short-term solution, as it may weaken the overall system security. To disable SELinux lockdown, edit the SELinux configuration file (usually located at /etc/selinux/config) and set the 'selinux' parameter to 'permissive' or 'disabled'. After making the changes, reboot the system for the modifications to take effect.
Conclusion
The buggy SELinux lockdown permission checks in the Kernel pose a significant security risk, potentially allowing attackers to bypass security restrictions and gain unauthorized access. It is crucial to update the Kernel to the fixed version v5.12.10 or later to mitigate this vulnerability. In the meantime, users can apply the temporary workaround of disabling SELinux lockdown, but this should only be considered as a short-term solution. For further support and assistance in vulnerability remediation, please contact DevNack.com.
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FAQ
The vulnerability allows attackers to bypass SELinux lockdown restrictions, potentially leading to privilege escalation, unauthorized network access, and information disclosure.
You can use the Vulert Playground (https://vulert.com/scanner) to check if your system is affected by this vulnerability. Simply upload your package-lock.json file and the playground will analyze it for any open-source vulnerabilities, including this one.
At the time of this report, there is no known public exploit for this vulnerability. However, it is advisable to apply the recommended fix as soon as possible to mitigate any potential risks.
Yes, you can temporarily disable SELinux lockdown as a workaround. However, this should only be considered as a short-term solution, as it may weaken the overall system security. It is strongly recommended to update the Kernel to the fixed version as soon as possible.
You can find more information about this vulnerability, including technical details and the fix, in the official Linux Kernel Git repository (https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/) and the vulnerability database maintained by the Cloud Security Alliance (https://github.com/cloudsecurityalliance/gsd-database).
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