RHSA-2021:0537HighCVSS 7.8

Red Hat Security Advisory: kernel-rt security and bug fix update

Published
February 16, 2021
Last Modified
November 5, 2026

🔗 CVE IDs covered (3)

CVE-2020-14351 →CVE-2020-25705 →CVE-2020-29661 →

📋 Description

CVE-2020-14351 — kernel: performance counters race condition use-after-free CVE-2020-25705 — kernel: ICMP rate limiting can be used for DNS poisoning attack CVE-2020-29661 — kernel: locking issue in drivers/tty/tty_jobctrl.c can lead to an use-after-free

🎯 Affected products32

  • Red Hat Enterprise Linux Real Time (v. 8)
  • Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-0:4.18.0-240.15.1.rt7.69.el8_3.src as a component of Red Hat Enterprise Linux Real Time (v. 8)
  • kernel-rt-0:4.18.0-240.15.1.rt7.69.el8_3.src as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time (v. 8)
  • kernel-rt-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-core-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time (v. 8)
  • kernel-rt-core-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-debug-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time (v. 8)
  • kernel-rt-debug-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-debug-core-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time (v. 8)
  • kernel-rt-debug-core-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-debug-debuginfo-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time (v. 8)
  • kernel-rt-debug-debuginfo-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-debug-devel-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time (v. 8)
  • kernel-rt-debug-devel-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-debug-kvm-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-debug-modules-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time (v. 8)
  • kernel-rt-debug-modules-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-debug-modules-extra-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time (v. 8)
  • kernel-rt-debug-modules-extra-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-debuginfo-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time (v. 8)
  • kernel-rt-debuginfo-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-debuginfo-common-x86_64-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time (v. 8)
  • kernel-rt-debuginfo-common-x86_64-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-devel-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time (v. 8)
  • kernel-rt-devel-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-kvm-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • kernel-rt-modules-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time (v. 8)
  • kernel-rt-modules-0:4.18.0-240.15.1.rt7.69.el8_3.x86_64 as a component of Red Hat Enterprise Linux Real Time for NFV (v. 8)
  • +2 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/11258 The system must be rebooted for this update to take effect. Workaround: While there is no way to disable the perf subsystem on Linux systems, reducing or removing users access to the perf events can effectively mitigate this flaw. Upstream kernel documentation has been written regarding this mechanism: https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html. Workaround: The mitigation is to disable ICMP destination unreachable messages. The commands to disable UDP port unreachable ICMP reply messages: iptables -I OUTPUT -p icmp --icmp-type destination-unreachable -j DROP service iptables save For additional information about "service iptables save" please read https://access.redhat.com/solutions/1597703 It is not recommended to apply this rule if host being used as forwarder (router) of IP packets. Or it is possible to use this firewall-cmd instead of iptables and the result is similar: firewall-cmd --permanent --direct --add-rule ipv4 filter OUTPUT 0 -p icmp --icmp-type destination-unreachable -j DROP Workaround: Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update as soon as possible.

🔗 References (6)