RHSA-2021:0152HighCVSS 8.1

Red Hat Security Advisory: dnsmasq security update

Published
January 19, 2021
Last Modified
November 5, 2026

🔗 CVE IDs covered (7)

CVE-2020-25683 →CVE-2020-25684 →CVE-2020-25685 →CVE-2020-25686 →CVE-2020-25687 →CVE-2020-25681 →CVE-2020-25682 →

📋 Description

CVE-2020-25681 — dnsmasq: heap-based buffer overflow in sort_rrset() when DNSSEC is enabled CVE-2020-25682 — dnsmasq: buffer overflow in extract_name() due to missing length check when DNSSEC is enabled CVE-2020-25683 — dnsmasq: heap-based buffer overflow with large memcpy in get_rdata() when DNSSEC is enabled 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-2020-25687 — dnsmasq: heap-based buffer overflow with large memcpy in sort_rrset() when DNSSEC is enabled

🎯 Affected products22

  • Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-0:2.79-6.el8_1.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-0:2.79-6.el8_1.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-0:2.79-6.el8_1.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-0:2.79-6.el8_1.1.src as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-0:2.79-6.el8_1.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-debuginfo-0:2.79-6.el8_1.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-debuginfo-0:2.79-6.el8_1.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-debuginfo-0:2.79-6.el8_1.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-debuginfo-0:2.79-6.el8_1.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-debugsource-0:2.79-6.el8_1.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-debugsource-0:2.79-6.el8_1.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-debugsource-0:2.79-6.el8_1.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-debugsource-0:2.79-6.el8_1.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-utils-0:2.79-6.el8_1.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-utils-0:2.79-6.el8_1.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-utils-0:2.79-6.el8_1.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-utils-0:2.79-6.el8_1.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-utils-debuginfo-0:2.79-6.el8_1.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-utils-debuginfo-0:2.79-6.el8_1.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-utils-debuginfo-0:2.79-6.el8_1.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)
  • dnsmasq-utils-debuginfo-0:2.79-6.el8_1.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 8.1)

✅ Remediation

For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 Workaround: The only known way to mitigate this flaw is to disable DNSSEC altogether, by removing the `--dnssec` command line option or the `dnssec` option from dnsmasq configuration file. 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.

🔗 References (11)