Critical Use-After-Free Vulnerability in Linux Kernel (CVE-2021-47639)
Summary
CVE-2021-47639: In the Linux kernel, the following vulnerability has been resolved: KVM: x86/mmu: Zap _all_ roots when unmapping gfn range in TDP MMU Zap both valid and invalid roots when zapping/unmapping a gfn range, as KVM must ensur... Affects linux versions < 5.17.3-1. Fixed in 5.17.3-1. How to fix ↓
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Background
The Linux kernel is the core component of many operating systems, providing essential services for hardware and software interaction. It is known for its robustness and versatility, supporting a wide range of devices and architectures. However, like any complex software, it is susceptible to vulnerabilities that can compromise system security. CVE-2021-47639 specifically affects the Kernel-based Virtual Machine (KVM) component, which allows multiple virtual machines to run on a single physical host. This vulnerability can lead to severe security risks if not addressed promptly.
Vulnerability Detail
CVE-2021-47639 is a use-after-free vulnerability in the KVM component of the Linux kernel. It arises from the failure to properly manage memory references when unmapping guest frame numbers (GFNs). Specifically, the TDP MMU does not zap invalid roots during mmu_notifier callbacks, which can lead to a situation where KVM holds references to freed pages. This can result in undefined behavior, including potential data corruption or system crashes. The vulnerability can be exploited if an attacker can manipulate the timing of memory operations, leading to critical security breaches.
How To Fix
Minimum fixed version
5.17.3-1
This is the first release that contains the fix.
sudo apt-get install --only-upgrade linuxTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
Currently, there are no specific workarounds mentioned for this vulnerability. The best course of action is to apply the available patch as soon as possible.
Conclusion
CVE-2021-47639 is a critical vulnerability in the Linux kernel's KVM component that can lead to serious security implications. It is essential to update to the patched version to protect your systems from potential exploitation. Regular monitoring and timely updates are vital in maintaining system security.
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FAQ
CVE-2021-47639 is a use-after-free vulnerability in the KVM component of the Linux kernel that can lead to severe security risks.
Exploitation of this vulnerability can lead to data corruption, system crashes, or unauthorized access to sensitive information.
If you are using an affected version of the Linux kernel (prior to 5.17.3-1), your system may be vulnerable. You can check your kernel version using the command 'uname -r'.
You can use Vulert to monitor and alert in real-time for open-source vulnerabilities in your software. Visit Vulert Scanner to check if your application is affected by this vulnerability.
While there are no specific workarounds, it is crucial to prioritize applying the patch as soon as possible to mitigate the risks associated with this vulnerability.
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