xt_TCPMSS buffer overflow bug

[Denys Fedoryshchenko]

Bug was reported in LKML here: https://lkml.org/lkml/2017/4/2/13
In few words - corrupted packet might be used to modify memory at router who has xt_TCPMSS used as iptables action.
This is really nasty bug, and can be triggered remotely by malicious person on anything that usually use this iptables action (PPPoE/PPTP-enabled ISP or VPN provider, for example).
This bug existed for several years, i guess.
I waited for a while since April, as it's already pushed to stable, and probably all distributions have it updated, so now it's time to do bugreport, to make sure it is really fixed everywhere.
Maybe worth to assign CVE for it?

[Seth Arnold (seth-arnold)]

Hello Denys,

Are fixes for this bug available?
Did you discover this bug?
Have you, or someone else, filed for a CVE for this issue yet?

Thanks

[Denys Fedoryshchenko (nuclearcat)]

Yes, already queued by Eric Dumazet in all stable since report in April
http://patchwork.ozlabs.org/patch/746618/

Yes, i did, but troubleshooting done and fix issued by Eric Dumazet.
Also there is chance exist that someone used it for malicious purposes "in wild" at that moment, as it appeared at peak time on ISP, in specific network with many users, while exactly same setup on other locations didn't had this issue. That was reason to enable KASAN and to search for it.

No CVE as far as i know, i just don't know how to do that. Not sure if Eric or netfilter developers (for example Pablo Neira Ayuso) filled anything.

[Seth Arnold (seth-arnold)]

Thanks Denys, I've asked MITRE for a CVE number for this issue.

[Seth Arnold (seth-arnold)]

Use CVE-2017-18017.

Thanks

[Denys Fedoryshchenko (nuclearcat)]

Perfect! Thanks a lot, now i have big reason to ask some sysadmins and vendors to upgrade their kernels.

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]

[Steve Beattie (sbeattie)]

Sorry, the kernel commit to fix this didn't pick up the launchpad bug number, so this bug didn't get auto-closed. It's been addressed in all Ubuntu releases e.g. https://usn.ubuntu.com/usn/usn-3583-1/ .
You can see the state at https://people.canonical.com/~ubuntu-security/cve/2017/CVE-2017-18017.html.

Thanks again for the report!