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Three related flaws were found in the Linux kernel’s handling of TCP Selective Acknowledgement (SACK) packets handling with low MSS size. These have been assigned the following CVEs: CVE-2019-11477 is considered an Important severity while CVE-2019-11478 and CVE-2019-11479 are considered a Moderate severity.
The following article outlines the details of the TCP SACK PANIC and how it impacts Sophos products.
TCP SACK PANIC kernel vulnerability fix released plan has been updated. Kindly check this link:
In reply to Shweta:
I posted a comment back to the advisory, but figured I would add it here to the community page as well.
I had a client this morning, whose machines would not grab an IPv4 address after I implemented the fix for the XG firewall last night.
The firewall is the dhcp server. it was showing leases assigned, but the computers were showing 'not connected'. I tried the typical netsh winsock and ip resets, but it was not until I reverted the change that the computers started working again. Strangely, even the Open-Mesh switch didn't show the PC as connected (at layer 2) until reverting the change.
In reply to JamesGolden:
Seems like you are affected by the DHCP issue.
Should not be related to this Workaround.
In reply to LuCar Toni:
Thanks LuCar, but it didn't fit any of the symptoms of the dhcp problem your referenced. As soon as I turn acknowledgements back on, the machines were able to grab an IP address and connect to the network.