CVE-2018-6764

util/virlog.c in libvirt does not properly determine the hostname on LXC container startup, which allows local guest OS users to bypass an intended container protection mechanism and execute arbitrary commands via a crafted NSS module.

Updated libvirt packages fix security vulnerabilities:

In virsh, the hostname could crafted maliciously with ssh arguments, which would be passed to ssh (bsc#1053600).

The default_tls_x509_verify (and related) parameters in qemu.conf control whether the TLS servers in QEMU request & verify certificates from clients. This works as a simple access control system for QEMU servers by requiring the CA to issue certs to permitted clients. This use of client certificates is disabled by default, since it requires extra work to issue client certificates. Unfortunately the libvirt code was using these configuration parameters when setting up both TLS clients and servers in QEMU. The result was that TLS clients for character devices and disk devices had verification turned off, meaning they would ignore any errors while validating the server certificate (CVE-2017-1000256).

An industry-wide issue was found in the way many modern microprocessor designs have implemented speculative execution of instructions (a commonly used performance optimization). There are three primary variants of the issue which differ in the way the speculative execution can be exploited. Variant CVE-2017-5715 triggers the speculative execution by utilizing branch target injection. It relies on the presence of a precisely-defined instruction sequence in the privileged code as well as the fact that memory accesses may cause allocation into the microprocessor's data cache even for speculatively executed instructions that never actually commit (retire). As a result, an unprivileged attacker could use this flaw to cross the syscall and guest/host boundaries and read privileged memory by conducting targeted cache side-channel attacks (CVE-2017-5715).

qemu/qemu_monitor.c in libvirt allows attackers to cause a denial of service (memory consumption) via a large QEMU reply (CVE-2018-5748).

It was discovered libvirt does not properly determine the hostname on LXC container startup, which allows local guest OS users to bypass an intended container protection mechanism and execute arbitrary commands via a crafted NSS module (CVE-2018-6764).

This update for libvirt fixes the following issues:

Security issues fixed:

• CVE-2017-5715: Fixes for speculative side channel attacks aka 'SpectreAttack' (var2) (bsc#1079869).
• CVE-2018-6764: Fixed guest executable code injection via libnss_dns.so loaded by libvirt_lxc before init (bsc#1080042).
• CVE-2018-1064: Fixed denial of service when reading from guest agent (bsc#1083625).

Non-security issues fixed:

• Error starting domain: internal error: No usable sysfs TPM cancel file could be found (bsc#1078808).
• SUSE Linux Enterprise 11 SP4 hvm converted to pvhvm. Unless vm memory is on gig boundary, vm won't boot (bsc#1082041).

This update for libvirt and virt-manager fixes the following issues:

Security issues fixed:

• CVE-2017-5715: Fixes for speculative side channel attacks aka 'SpectreAttack' (var2) (bsc#1079869).
• CVE-2018-6764: Fixed guest executable code injection via libnss_dns.so loaded by libvirt_lxc before init (bsc#1080042).
• CVE-2018-1064: Fixed denial of service when reading from guest agent (bsc#1083625).

Non-security issues fixed in libvirt:

• bsc#1070615: Fixed TPM device passthrough failure on kernels >= 4.0.
• bsc#1082041: SUSE Linux Enterprise 11 SP4 hvm converted to pvhvm. Unless vm memory is on gig boundary, vm won't boot.
• bsc#1082161: Unable to change RTC basis or adjustment for Xen HVM guests using libvirt.

Non-security issues fixed in virt-manager:

• bsc#1086038: VM guests cannot be properly installed with virt-install
• bsc#1067018: KVM Guest creation failed - Property .cmt not found
• bsc#1054986: Fix openSUSE 15.0 detection. It has no content file or .treeinfo file
• bsc#1085757: Fallback to latest version of openSUSE when opensuse-unknown is detected for the ISO

Vivian Zhang and Christoph Anton Mitterer discovered that libvirt incorrectly disabled password authentication when the VNC password was set to an empty string. A remote attacker could possibly use this issue to bypass authentication, contrary to expectations. This issue only affected Ubuntu 14.04 LTS and Ubuntu 16.04 LTS. (CVE-2016-5008)

Daniel P. Berrange discovered that libvirt incorrectly handled validating SSL/TLS certificates. A remote attacker could possibly use this issue to obtain sensitive information. This issue only affected Ubuntu 17.10. (CVE-2017-1000256)

Daniel P. Berrange and Peter Krempa discovered that libvirt incorrectly handled large QEMU replies. An attacker could possibly use this issue to cause libvirt to crash, resulting in a denial of service. (CVE-2018-5748)

Pedro Sampaio discovered that libvirt incorrectly handled the libnss_dns.so module. An attacker in a libvirt_lxc session could possibly use this issue to execute arbitrary code. This issue only affected Ubuntu 16.04 LTS and Ubuntu 17.10. (CVE-2018-6764)