The x86 emulator in KVM 83, when a guest is configured for Symmetric Multiprocessing (SMP), does not properly restrict writing of segment selectors to segment registers, which might allow guest OS users to cause a denial of service (guest OS crash) or gain privileges on the guest OS by leveraging access to a (1) IO port or (2) MMIO region, and replacing an instruction in between emulator entry and instruction fetch.

From Red Hat Security Advisory 2010:0126 :

Updated kvm packages that fix two security issues and two bugs are now available for Red Hat Enterprise Linux 5.

This update has been rated as having important security impact by the Red Hat Security Response Team.

KVM (Kernel-based Virtual Machine) is a full virtualization solution for Linux on AMD64 and Intel 64 systems. KVM is a Linux kernel module built for the standard Red Hat Enterprise Linux kernel.

A flaw was found in the way the x86 emulator loaded segment selectors (used for memory segmentation and protection) into segment registers.
In some guest system configurations, an unprivileged guest user could leverage this flaw to crash the guest or possibly escalate their privileges within the guest. (CVE-2010-0419)

The x86 emulator implementation was missing a check for the Current Privilege Level (CPL) while accessing debug registers. An unprivileged user in a guest could leverage this flaw to crash the guest.
(CVE-2009-3722)

This update also fixes the following bugs :

With Red Hat Enterprise Virtualization, the virtio_blk_dma_restart_bh() function was previously used to handle write errors; however, a bug fix provided by the RHSA-2009:1659 update meant that read errors would also have to be handled by this function.
The function was not updated for this, causing read errors to be resubmitted as writes. This caused guest image corruption in some cases.

Additionally, the return values of the bdrv_aio_write() and bdrv_aio_read() functions were ignored. If an immediate failure occurred in one of these functions, errors would be missed and the guest could hang or read corrupted data. (BZ#562776)

All KVM users should upgrade to these updated packages, which contain backported patches to resolve these issues. Note: The procedure in the Solution section must be performed before this update will take effect.

Updated kvm packages that fix two security issues and two bugs are now available for Red Hat Enterprise Linux 5.

This update has been rated as having important security impact by the Red Hat Security Response Team.

KVM (Kernel-based Virtual Machine) is a full virtualization solution for Linux on AMD64 and Intel 64 systems. KVM is a Linux kernel module built for the standard Red Hat Enterprise Linux kernel.

A flaw was found in the way the x86 emulator loaded segment selectors (used for memory segmentation and protection) into segment registers.
In some guest system configurations, an unprivileged guest user could leverage this flaw to crash the guest or possibly escalate their privileges within the guest. (CVE-2010-0419)

The x86 emulator implementation was missing a check for the Current Privilege Level (CPL) while accessing debug registers. An unprivileged user in a guest could leverage this flaw to crash the guest.
(CVE-2009-3722)

This update also fixes the following bugs :

With Red Hat Enterprise Virtualization, the virtio_blk_dma_restart_bh() function was previously used to handle write errors; however, a bug fix provided by the RHSA-2009:1659 update meant that read errors would also have to be handled by this function.
The function was not updated for this, causing read errors to be resubmitted as writes. This caused guest image corruption in some cases.

Additionally, the return values of the bdrv_aio_write() and bdrv_aio_read() functions were ignored. If an immediate failure occurred in one of these functions, errors would be missed and the guest could hang or read corrupted data. (BZ#562776)

All KVM users should upgrade to these updated packages, which contain backported patches to resolve these issues. Note: The procedure in the Solution section must be performed before this update will take effect.

CVE-2009-3722 KVM: Check cpl before emulating debug register access

CVE-2010-0419 kvm: emulator privilege escalation segment selector check

A flaw was found in the way the x86 emulator loaded segment selectors (used for memory segmentation and protection) into segment registers.
In some guest system configurations, an unprivileged guest user could leverage this flaw to crash the guest or possibly escalate their privileges within the guest. (CVE-2010-0419)

The x86 emulator implementation was missing a check for the Current Privilege Level (CPL) while accessing debug registers. An unprivileged user in a guest could leverage this flaw to crash the guest.
(CVE-2009-3722)

This update also fixes the following bugs :

The return values of the bdrv_aio_write() and bdrv_aio_read() functions were ignored. If an immediate failure occurred in one of these functions, errors would be missed and the guest could hang or read corrupted data. (BZ#562776)

The following procedure must be performed before this update will take effect :

1) Stop all KVM guest virtual machines.

2) Either reboot the hypervisor machine or, as the root user, remove (using 'modprobe -r [module]') and reload (using 'modprobe [module]') all of the following modules which are currently running (determined using 'lsmod'): kvm, ksm, kvm-intel or kvm-amd.

3) Restart the KVM guest virtual machines.

USN-947-1 fixed vulnerabilities in the Linux kernel. Fixes for CVE-2010-0419 caused failures when using KVM in certain situations.
This update reverts that fix until a better solution can be found.

We apologize for the inconvenience.

It was discovered that the Linux kernel did not correctly handle memory protection of the Virtual Dynamic Shared Object page when running a 32-bit application on a 64-bit kernel. A local attacker could exploit this to cause a denial of service. (Only affected Ubuntu 6.06 LTS.) (CVE-2009-4271)

It was discovered that the r8169 network driver did not correctly check the size of Ethernet frames. A remote attacker could send specially crafted traffic to crash the system, leading to a denial of service. (CVE-2009-4537)

Wei Yongjun discovered that SCTP did not correctly validate certain chunks. A remote attacker could send specially crafted traffic to monopolize CPU resources, leading to a denial of service. (Only affected Ubuntu 6.06 LTS.) (CVE-2010-0008)

It was discovered that KVM did not correctly limit certain privileged IO accesses on x86. Processes in the guest OS with access to IO regions could gain further privileges within the guest OS. (Did not affect Ubuntu 6.06 LTS.) (CVE-2010-0298, CVE-2010-0306, CVE-2010-0419)

Evgeniy Polyakov discovered that IPv6 did not correctly handle certain TUN packets. A remote attacker could exploit this to crash the system, leading to a denial of service.
(Only affected Ubuntu 8.04 LTS.) (CVE-2010-0437)

Sachin Prabhu discovered that GFS2 did not correctly handle certain locks. A local attacker with write access to a GFS2 filesystem could exploit this to crash the system, leading to a denial of service. (CVE-2010-0727)

Jamie Strandboge discovered that network virtio in KVM did not correctly handle certain high-traffic conditions. A remote attacker could exploit this by sending specially crafted traffic to a guest OS, causing the guest to crash, leading to a denial of service. (Only affected Ubuntu 8.04 LTS.) (CVE-2010-0741)

Marcus Meissner discovered that the USB subsystem did not correctly handle certain error conditions. A local attacker with access to a USB device could exploit this to read recently used kernel memory, leading to a loss of privacy and potentially root privilege escalation. (CVE-2010-1083)

Neil Brown discovered that the Bluetooth subsystem did not correctly handle large amounts of traffic. A physically proximate remote attacker could exploit this by sending specially crafted traffic that would consume all available system memory, leading to a denial of service. (Ubuntu 6.06 LTS and 10.04 LTS were not affected.) (CVE-2010-1084)

Jody Bruchon discovered that the sound driver for the AMD780V did not correctly handle certain conditions. A local attacker with access to this hardward could exploit the flaw to cause a system crash, leading to a denial of service.
(CVE-2010-1085)

Ang Way Chuang discovered that the DVB driver did not correctly handle certain MPEG2-TS frames. An attacker could exploit this by delivering specially crafted frames to monopolize CPU resources, leading to a denial of service.
(Ubuntu 10.04 LTS was not affected.) (CVE-2010-1086)

Trond Myklebust discovered that NFS did not correctly handle truncation under certain conditions. A local attacker with write access to an NFS share could exploit this to crash the system, leading to a denial of service. (Ubuntu 10.04 LTS was not affected.) (CVE-2010-1087)

Al Viro discovered that automount of NFS did not correctly handle symlinks under certain conditions. A local attacker could exploit this to crash the system, leading to a denial of service. (Ubuntu 6.06 LTS and Ubuntu 10.04 LTS were not affected.) (CVE-2010-1088)

Matt McCutchen discovered that ReiserFS did not correctly protect xattr files in the .reiserfs_priv directory. A local attacker could exploit this to gain root privileges or crash the system, leading to a denial of service. (CVE-2010-1146)

Eugene Teo discovered that CIFS did not correctly validate arguments when creating new files. A local attacker could exploit this to crash the system, leading to a denial of service, or possibly gain root privileges if mmap_min_addr was not set. (CVE-2010-1148)

Catalin Marinas and Tetsuo Handa discovered that the TTY layer did not correctly release process IDs. A local attacker could exploit this to consume kernel resources, leading to a denial of service. (CVE-2010-1162)

Neil Horman discovered that TIPC did not correctly check its internal state. A local attacker could send specially crafted packets via AF_TIPC that would cause the system to crash, leading to a denial of service. (Ubuntu 6.06 LTS was not affected.) (CVE-2010-1187)

Masayuki Nakagawa discovered that IPv6 did not correctly handle certain settings when listening. If a socket were listening with the IPV6_RECVPKTINFO flag, a remote attacker could send specially crafted traffic that would cause the system to crash, leading to a denial of service. (Only Ubuntu 6.06 LTS was affected.) (CVE-2010-1188)

Oleg Nesterov discovered that the Out-Of-Memory handler did not correctly handle certain arrangements of processes. A local attacker could exploit this to crash the system, leading to a denial of service. (CVE-2010-1488).

Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

It was discovered that the Linux kernel did not correctly handle memory protection of the Virtual Dynamic Shared Object page when running a 32-bit application on a 64-bit kernel. A local attacker could exploit this to cause a denial of service. (Only affected Ubuntu 6.06 LTS.) (CVE-2009-4271)

It was discovered that the r8169 network driver did not correctly check the size of Ethernet frames. A remote attacker could send specially crafted traffic to crash the system, leading to a denial of service. (CVE-2009-4537)

Wei Yongjun discovered that SCTP did not correctly validate certain chunks. A remote attacker could send specially crafted traffic to monopolize CPU resources, leading to a denial of service. (Only affected Ubuntu 6.06 LTS.) (CVE-2010-0008)

It was discovered that KVM did not correctly limit certain privileged IO accesses on x86. Processes in the guest OS with access to IO regions could gain further privileges within the guest OS. (Did not affect Ubuntu 6.06 LTS.) (CVE-2010-0298, CVE-2010-0306, CVE-2010-0419)

Evgeniy Polyakov discovered that IPv6 did not correctly handle certain TUN packets. A remote attacker could exploit this to crash the system, leading to a denial of service. (Only affected Ubuntu 8.04 LTS.) (CVE-2010-0437)

Sachin Prabhu discovered that GFS2 did not correctly handle certain locks. A local attacker with write access to a GFS2 filesystem could exploit this to crash the system, leading to a denial of service.
(CVE-2010-0727)

Jamie Strandboge discovered that network virtio in KVM did not correctly handle certain high-traffic conditions. A remote attacker could exploit this by sending specially crafted traffic to a guest OS, causing the guest to crash, leading to a denial of service. (Only affected Ubuntu 8.04 LTS.) (CVE-2010-0741)

Marcus Meissner discovered that the USB subsystem did not correctly handle certain error conditions. A local attacker with access to a USB device could exploit this to read recently used kernel memory, leading to a loss of privacy and potentially root privilege escalation.
(CVE-2010-1083)

Neil Brown discovered that the Bluetooth subsystem did not correctly handle large amounts of traffic. A physically proximate remote attacker could exploit this by sending specially crafted traffic that would consume all available system memory, leading to a denial of service. (Ubuntu 6.06 LTS and 10.04 LTS were not affected.) (CVE-2010-1084)

Jody Bruchon discovered that the sound driver for the AMD780V did not correctly handle certain conditions. A local attacker with access to this hardward could exploit the flaw to cause a system crash, leading to a denial of service. (CVE-2010-1085)

Ang Way Chuang discovered that the DVB driver did not correctly handle certain MPEG2-TS frames. An attacker could exploit this by delivering specially crafted frames to monopolize CPU resources, leading to a denial of service. (Ubuntu 10.04 LTS was not affected.) (CVE-2010-1086)

Trond Myklebust discovered that NFS did not correctly handle truncation under certain conditions. A local attacker with write access to an NFS share could exploit this to crash the system, leading to a denial of service. (Ubuntu 10.04 LTS was not affected.) (CVE-2010-1087)

Al Viro discovered that automount of NFS did not correctly handle symlinks under certain conditions. A local attacker could exploit this to crash the system, leading to a denial of service. (Ubuntu 6.06 LTS and Ubuntu 10.04 LTS were not affected.) (CVE-2010-1088)

Matt McCutchen discovered that ReiserFS did not correctly protect xattr files in the .reiserfs_priv directory. A local attacker could exploit this to gain root privileges or crash the system, leading to a denial of service. (CVE-2010-1146)

Eugene Teo discovered that CIFS did not correctly validate arguments when creating new files. A local attacker could exploit this to crash the system, leading to a denial of service, or possibly gain root privileges if mmap_min_addr was not set. (CVE-2010-1148)

Catalin Marinas and Tetsuo Handa discovered that the TTY layer did not correctly release process IDs. A local attacker could exploit this to consume kernel resources, leading to a denial of service.
(CVE-2010-1162)

Neil Horman discovered that TIPC did not correctly check its internal state. A local attacker could send specially crafted packets via AF_TIPC that would cause the system to crash, leading to a denial of service. (Ubuntu 6.06 LTS was not affected.) (CVE-2010-1187)

Masayuki Nakagawa discovered that IPv6 did not correctly handle certain settings when listening. If a socket were listening with the IPV6_RECVPKTINFO flag, a remote attacker could send specially crafted traffic that would cause the system to crash, leading to a denial of service. (Only Ubuntu 6.06 LTS was affected.) (CVE-2010-1188)

Oleg Nesterov discovered that the Out-Of-Memory handler did not correctly handle certain arrangements of processes. A local attacker could exploit this to crash the system, leading to a denial of service. (CVE-2010-1488).

Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Several local vulnerabilities have been discovered in kvm, a full virtualization system. The Common Vulnerabilities and Exposures project identifies the following problems :

  - CVE-2010-0298 CVE-2010-0306     Gleb Natapov discovered issues in the KVM subsystem     where missing permission checks (CPL/IOPL) permit a user     in a guest system to denial of service a guest (system     crash) or gain escalated privileges with the guest.

  - CVE-2010-0309     Marcelo Tosatti fixed an issue in the PIT emulation code     in the KVM subsystem that allows privileged users in a     guest domain to cause a denial of service (crash) of the     host system.

  - CVE-2010-0419     Paolo Bonzini found a bug in KVM that can be used to     bypass proper permission checking while loading segment     selectors. This potentially allows privileged guest     users to execute privileged instructions on the host     system.

ID	Name	Product	Family	Severity
68005	Oracle Linux 5 : kvm (ELSA-2010-0126)	Nessus	Oracle Linux Local Security Checks	high
63920	RHEL 5 : kvm (RHSA-2010:0126)	Nessus	Red Hat Local Security Checks	high
60740	Scientific Linux Security Update : kvm on SL5.4 x86_64	Nessus	Scientific Linux Local Security Checks	high
46811	Ubuntu 10.04 LTS : linux regression (USN-947-2)	Nessus	Ubuntu Local Security Checks	high
46810	Ubuntu 6.06 LTS / 8.04 LTS / 9.04 / 9.10 / 10.04 LTS : linux, linux-source-2.6.15 vulnerabilities (USN-947-1)	Nessus	Ubuntu Local Security Checks	high
45026	Debian DSA-2010-1 : kvm - privilege escalation/denial of service	Nessus	Debian Local Security Checks	medium
44969	CentOS 5 : kvm (CESA-2010:0126)	Nessus	CentOS Local Security Checks	high

Detections

Analytics

CVE-2010-0419

critical

Tenable Plugins

high

high

high

high

high

medium

high