First published: Tue Jan 27 2015(Updated: )
It was found that the Linux kernel KVM subsystem's sysenter instruction emulation was not sufficient. An unprivileged guest user could use this flaw to escalate their privileges by tricking the hypervisor to emulate a SYSENTER instruction in 16-bit mode, if the guest OS does not initialize the SYSENTER MSRs. Please note that the Red Hat Enterprise Linux with KVM certified guest operating systems do initialize the SYSENTER MSRs and are thus not vulnerable to this issue when running on KVM hypervisor. References: <a href="http://www.openwall.com/lists/oss-security/2015/01/27/6">http://www.openwall.com/lists/oss-security/2015/01/27/6</a> Upstream patch: <a href="http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=f3747379accba8e95d70cec0eae0582c8c182050">http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=f3747379accba8e95d70cec0eae0582c8c182050</a> Acknowledgements: Red Hat would like to thank Nadav Amit for reporting this issue.
Credit: secalert@redhat.com
Affected Software | Affected Version | How to fix |
---|---|---|
Linux Kernel | <3.18.5 | |
Ubuntu Linux | =12.04 | |
Ubuntu Linux | =14.04 | |
Ubuntu Linux | =14.10 | |
Debian Debian Linux | =7.0 | |
Debian Debian Linux | =8.0 | |
Oracle Linux | =5 | |
Oracle Linux | =7 | |
redhat enterprise Linux desktop | =6.0 | |
redhat enterprise Linux server | =6.0 | |
redhat enterprise Linux workstation | =6.0 | |
debian/linux | 5.10.223-1 5.10.226-1 6.1.123-1 6.1.119-1 6.12.11-1 6.12.12-1 |
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CVE-2015-0239 has a medium severity level as it allows unprivileged users to escalate privileges on affected systems.
To fix CVE-2015-0239, update the Linux kernel to version 3.18.5 or later versions provided by your distribution.
CVE-2015-0239 affects various versions of the Linux kernel, particularly those prior to 3.18.5, and specific distributions like Ubuntu, Debian, and Red Hat.
CVE-2015-0239 requires an attacker to have an unprivileged account on the guest system, so it cannot be exploited remotely.
As of now, there are no public exploits available for CVE-2015-0239, but the vulnerability itself poses a significant risk if left unpatched.