RHSA-2021:0395HighCVSS 7.8

Red Hat Security Advisory: RHV-H security, bug fix, enhancement update (redhat-virtualization-host) 4.3.13

Published
February 3, 2021
Last Modified
November 5, 2026

🔗 CVE IDs covered (4)

CVE-2020-25685 →CVE-2020-25686 →CVE-2021-3156 →CVE-2020-25684 →

📋 Description

CVE-2020-25684 — dnsmasq: loose address/port check in reply_query() makes forging replies easier for an off-path attacker CVE-2020-25685 — dnsmasq: loose query name check in reply_query() makes forging replies easier for an off-path attacker CVE-2020-25686 — dnsmasq: multiple queries forwarded for the same name makes forging replies easier for an off-path attacker CVE-2021-3156 — sudo: Heap buffer overflow in argument parsing

🎯 Affected products37

  • RHEL 7-based RHEV-H for RHEV 4 (build requirements)
  • Red Hat Virtualization 4 Hypervisor for RHEL 7
  • Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • redhat-release-virtualization-host-0:4.3.13-2.el7ev.src as a component of RHEL 7-based RHEV-H for RHEV 4 (build requirements)
  • redhat-release-virtualization-host-0:4.3.13-2.el7ev.x86_64 as a component of RHEL 7-based RHEV-H for RHEV 4 (build requirements)
  • redhat-virtualization-host-0:4.3.13-20210127.0.el7_9.src as a component of RHEL 7-based RHEV-H for RHEV 4 (build requirements)
  • redhat-virtualization-host-0:4.3.13-20210127.0.el7_9.src as a component of Red Hat Virtualization 4 Hypervisor for RHEL 7
  • redhat-virtualization-host-image-update-0:4.3.13-20210127.0.el7_9.noarch as a component of RHEL 7-based RHEV-H for RHEV 4 (build requirements)
  • redhat-virtualization-host-image-update-0:4.3.13-20210127.0.el7_9.noarch as a component of Red Hat Virtualization 4 Hypervisor for RHEL 7
  • redhat-virtualization-host-image-update-placeholder-0:4.3.13-2.el7ev.noarch as a component of RHEL 7-based RHEV-H for RHEV 4 (build requirements)
  • vdsm-0:4.30.51-1.el7ev.ppc64le as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-0:4.30.51-1.el7ev.src as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-0:4.30.51-1.el7ev.x86_64 as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-api-0:4.30.51-1.el7ev.noarch as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-client-0:4.30.51-1.el7ev.noarch as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-common-0:4.30.51-1.el7ev.noarch as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-gluster-0:4.30.51-1.el7ev.ppc64le as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-gluster-0:4.30.51-1.el7ev.x86_64 as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-hook-checkips-0:4.30.51-1.el7ev.ppc64le as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-hook-checkips-0:4.30.51-1.el7ev.x86_64 as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-hook-cpuflags-0:4.30.51-1.el7ev.noarch as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-hook-ethtool-options-0:4.30.51-1.el7ev.noarch as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-hook-extra-ipv4-addrs-0:4.30.51-1.el7ev.ppc64le as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-hook-extra-ipv4-addrs-0:4.30.51-1.el7ev.x86_64 as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-hook-fcoe-0:4.30.51-1.el7ev.noarch as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-hook-localdisk-0:4.30.51-1.el7ev.noarch as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-hook-macspoof-0:4.30.51-1.el7ev.noarch as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-hook-nestedvt-0:4.30.51-1.el7ev.noarch as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-hook-openstacknet-0:4.30.51-1.el7ev.noarch as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • vdsm-hook-vhostmd-0:4.30.51-1.el7ev.noarch as a component of Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts
  • +7 more not shown

✅ Remediation

For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/2974891 Workaround: The impact of this flaw can be reduced by disabling the dnsmasq cache by adding `--cache-size=0` when calling dnsmasq or by adding a line with `cache-size=0` to the dnsmasq configuration file (/etc/dnsmasq.conf by default). When using Red Hat Enterprise Linux 8.3 with libvirt through a virt:rhel module, use `virsh net-edit <network-name>` and reference https://libvirt.org/formatnetwork.html#elementsNamespaces to add the suggested option `cache-size=0`. There is no way to customize the dnsmasq configuration generated by libvirt, when using versions of Red Hat Enterprise Linux prior to version 8.3. If dnsmasq is being run through NetworkManager, create a new file in /etc/NetworkManager/dnsmasq.d/ and add `cache-size=0` to it. In all cases, by disabling the cache, you may experience a performance loss in your environment due to all DNS queries being forwarded to the upstream servers. Please evaluate if the mitigation is appropriate for the system’s environment before applying. Workaround: The impact of this flaw can be reduced by disabling the dnsmasq cache by adding `--cache-size=0` when calling dnsmasq or by adding a line with `cache-size=0` to the dnsmasq configuration file (/etc/dnsmasq.conf by default). When using Red Hat Enterprise Linux 8.3 with libvirt through a virt:rhel module, use `virsh net-edit <network-name>` and reference https://libvirt.org/formatnetwork.html#elementsNamespaces to add the suggested option `cache-size=0`. There is no way to customize the dnsmasq configuration generated by libvirt, when using versions of Red Hat Enterprise Linux prior to version 8.3. If dnsmasq is being run through NetworkManager, create a new file in /etc/NetworkManager/dnsmasq.d/ and add `cache-size=0` to it. In all cases, by disabling the cache, you may experience a performance loss in your environment due to all DNS queries being forwarded to the upstream servers. Please evaluate if the mitigation is appropriate for the system’s environment before applying. Workaround: Red Hat Product Security strongly recommends customers to update to fixed sudo packages once they are available. For customers who cannot update immediately, the following interim partial mitigation using systemtap is suggested: 1. Install required systemtap packages and dependencies: ``` systemtap yum-utils kernel-devel-"$(uname -r)" ``` Then for RHEL 7 install kernel debuginfo, using: ``` debuginfo-install -y kernel-"$(uname -r)" ``` Then for RHEL 8 & 6 install sudo debuginfo, using: ``` debuginfo-install sudo ``` 2. Create the following systemtap script: (call the file as sudoedit-block.stap) ``` probe process("/usr/bin/sudo").function("main") { command = cmdline_args(0,0,""); if (isinstr(command, "edit")) { raise(9); } } ``` 3. Install the script using the following command: (using root) ``` # nohup stap -g sudoedit-block.stap & ``` (This should output the PID number of the systemtap script) This script will cause the vulnerable sudoedit binary to stop working. The sudo command will still work as usual. The above change does not persist across reboots and must be applied after each reboot. Please consult How to make a systemtap kernel module load persistently across reboots? (https://access.redhat.com/solutions/5752521) to learn how to turn this into a service managed by initd. 4. Once the new fixed packages are installed, the systemtap script can be removed by killing the systemtap process. For example, by using: ``` # kill -s SIGTERM 7590 ``` (where 7590 is the PID of the systemtap process)

🔗 References (11)