NAM Access Gateway Appliance TCP MSS CVE-2019-11479

  • 7023990
  • 05-Jul-2019
  • 22-Jul-2019


  • Access Manager Gateway Appliance 4.4
  • Access Manager Gateway Appliance 4.5
  • Access Manager Appliance 4.4
  • Access Manager Appliance 4.5


  • Jonathan Looney discovered that the Linux kernel default MSS is hard-coded to 48 bytes. This allows a remote peer to fragment TCP resend queues significantly more than if a larger MSS were enforced. A remote attacker could use this to cause a denial of service. This has been fixed in stable kernel releases 4.4.182, 4.9.182, 4.14.127, 4.19.52, 5.1.11, and is fixed in commits 967c05aee439e6e5d7d805e195b3a20ef5c433d6 and 5f3e2bf008c2221478101ee72f5cb4654b9fc363.

  • The NAM Access Gateway Appliance Version 4.5 update channel provides "kernel-default-4.4.180-94.97.1" which includes CVE-2019-11479. See :

  • The NAM Access Gateway Appliance 4.4.4 and the NAM Appliance (Single Box Solution) update channel provides "kernel-default-3.0.101-108.98.1" which includes CVE-2019-11479. See :


  • run the channel update in order to install the kernel version including the fix

Additional Information

You can verify the if a given kernel includes the fix by using for example:

rpm -q --changelog kernel-default-3.0.101-108.98.1 | grep CVE-2019-11479
  patches.fixes/tcp-add-tcp_min_snd_mss-sysctl.patch (add CVE-2019-11479)
  patches.fixes/tcp-enforce-tcp_min_snd_mss-in-tcp_mtu_probing.patch (add CVE-2019-11479)