[Dnsmasq-discuss] CVE-2017-14495 PoC causes high CPU usage and denial of service against dnsmasq v2.79

Mouath Ibrahim dnsmasq at mouath.com
Tue Oct 9 09:45:39 BST 2018


On Monday, October 8, 2018 2:24:59 AM CDT Kevin Darbyshire-Bryant wrote:
> > On 8 Oct 2018, at 02:58, Mouath Ibrahim <dnsmasq at mouath.com> wrote:
> > 
> > Hello,
> > 
> > I ran the PoC supplied by Google research team found here:
> > https://github.com/
> > google/security-research-pocs/blob/master/vulnerabilities/dnsmasq/
> > CVE-2017-14495.py
> > 
> > and noticed immediately that dnsmasq process uses up 100% CPU usage and
> > stops responding to queries short after based on the original CVE the
> > effect was high memory usage but in this cause it was not.
> > 
> > note dnsmasq didn't have any of these options set "--add-mac, --add-cpe-id
> > or --add-subnet".
> > 
> > Regards,
> > Mouath Ibrahim
> 
> I am unable to reproduce.  Against which version/s of dnsmasq did you try?
> 
> 
> Cheers,
> 
> Kevin D-B
> 
> 012C ACB2 28C6 C53E 9775  9123 B3A2 389B 9DE2 334A

I'm using 2.79 on arch linux machine with an i5 @ 2.53GHz
and a patched version from the Pi-Hole team v4.0 that is a forked from 2.79, 
this one is running on my raspberry pi 3

I've also tested it on a manjaro linux and ended up crashing kde for me, 
something with the bus could be not related.

I mainly run unbound as a recursive resolver so I thought that could be the 
cause but it wasn't. I set up both machines (pi and arch) to use 8.8.8.8 and 
1.1.1.1 as upstream and ran 3rd on my desktop to forward queries to both of 
them.

dnsmasq couldn't resolve anything and eventually i had to stop it. cpu 
overheats quick.

wish I can give more details, but I'm no expert.

Mouath






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