CVE-2019-11477 aka SACK

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lazardo
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Joined: 17 Apr 2014
Posts: 97
Location: SF Bay Area

PostPosted: Wed Jun 19, 2019 17:33    Post subject: CVE-2019-11477 aka SACK Reply with quote
I inserted the rule below using the GUI Admin->Commands->firewall, then 'save firewall'.
Code:
iptables -I INPUT 2 -p tcp -m tcpmss --mss 1:500 -j DROP

Details: https://github.com/Netflix/security-bulletins/blob/master/advisories/third-party/2019-001/block-low-mss/iptables.txt

Update: The iptables rule above is the only solution available to releases LESS THAN 40058, eg, all older installs. Unless you compile your own of course.

Redhat has further modified the above Netflix mitigation:
https://access.redhat.com/security/vulnerabilities/tcpsack
Code:
iptables -I INPUT -p tcp --tcp-flags SYN SYN -m tcpmss --mss 1:500 -j DROP


Last edited by lazardo on Thu Jun 20, 2019 22:19; edited 2 times in total
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kernel-panic69
DD-WRT Guru


Joined: 08 May 2018
Posts: 1558
Location: Texas, USA

PostPosted: Wed Jun 19, 2019 17:43    Post subject: Reply with quote
https://github.com/Netflix/security-bulletins/blob/master/advisories/third-party/2019-001.md <-- actual advisories, which give workarounds and kernel patches.
jwh7
DD-WRT Guru


Joined: 25 Oct 2013
Posts: 2293
Location: Indy

PostPosted: Wed Jun 19, 2019 19:26    Post subject: Reply with quote
Fyi - CVE-2019-11478 is in r40058 (and r40060). And there is also CVE-2019-11479, fwiw.
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kernel-panic69
DD-WRT Guru


Joined: 08 May 2018
Posts: 1558
Location: Texas, USA

PostPosted: Thu Jun 20, 2019 2:10    Post subject: Reply with quote
jwh7 wrote:
Fyi - CVE-2019-11478 is in r40058 (and r40060). And there is also CVE-2019-11479, fwiw.


I didn't look at the patches close enough, thanks for the confirm.
Mile-Lile
DD-WRT Guru


Joined: 24 Feb 2013
Posts: 1436
Location: Belgrade

PostPosted: Thu Jun 20, 2019 10:17    Post subject: Reply with quote
Code:
iptables -t mangle -I PREROUTING -p tcp -m conntrack --ctstate NEW -m tcpmss ! --mss 536:65535 -j DROP
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