Kernel Samepage Merging Vulnerability in Linux Packages: CVE-2015-2877
Summary
UBUNTU-CVE-2015-2877: DISPUTED Kernel Samepage Merging (KSM) in the Linux kernel 2.6.32 through 4.x does not prevent use of a write-timing side channel, which allows guest OS users to defeat the ASLR protection mechanism on other guest OS ins... Affects linux versions 3.11.0-12.19 – 3.13.0-98.145. No fix is published. How to fix ↓
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Background
The Linux kernel is a core component of the operating system that manages hardware resources and provides essential services for applications. It supports various functionalities, including process management, memory management, and device control. The vulnerability in question affects multiple Linux packages across different Ubuntu LTS versions, specifically those utilizing Kernel Samepage Merging (KSM) for memory optimization. This feature allows multiple virtual machines to share identical memory pages, which can lead to potential security risks if not properly managed.
Vulnerability Detail
The vulnerability, identified as CVE-2015-2877, arises from the Kernel Samepage Merging (KSM) feature in the Linux kernel versions 2.6.32 through 4.x. It does not adequately prevent the exploitation of a write-timing side channel, enabling malicious users in one guest OS to compromise the Address Space Layout Randomization (ASLR) protections of other guest OS instances. This Cross-VM ASL Introspection (CAIN) attack can lead to unauthorized information disclosure, potentially allowing attackers to infer sensitive data from other virtual machines. The vendor has noted that if organizations are concerned about this attack vector, they should consider disabling deduplication.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
As a workaround, if you are concerned about the vulnerability, you can disable the KSM feature by executing the following command:
echo 0 | sudo tee /sys/kernel/mm/ksm/run
This command will stop KSM from running, thereby mitigating the risk of the vulnerability, although it may lead to increased memory usage.
Conclusion
CVE-2015-2877 is a significant vulnerability affecting various Linux packages that utilize Kernel Samepage Merging. Organizations should prioritize updating their systems to patched versions or implement workarounds to mitigate potential risks. Regular monitoring for vulnerabilities using tools like Vulert can help maintain security in open-source software.
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FAQ
CVE-2015-2877 is a vulnerability in the Linux kernel that allows guest OS users to exploit a write-timing side channel, potentially compromising the ASLR protections of other guest OS instances.
The vulnerability affects several packages including linux, linux-aws, linux-azure, and others across Ubuntu LTS versions 14.04, 16.04, and 18.04.
You can use Vulert, which monitors open-source vulnerabilities in your software using a manifest file like package-lock.json. You can check your application at Vulert Scanner without needing to sign up.
The CVSS score for CVE-2015-2877 is 3.3, indicating a low severity level.
If updating is not possible, consider disabling KSM as a temporary workaround to mitigate the risk associated with this vulnerability.
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