Linux Kernel Default MSS Hard-Coded to 48 Bytes Denial of Service Vulnerability

CVE-2019-11479 · HIGH Severity

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

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