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Date: Sun, 7 May 2017 20:47:39 +0200
From: Salvatore Bonaccorso <carnil@...ian.org>
To: oss-security@...ts.openwall.com
Subject: Re: rpcbomb: remote rpcbind denial-of-service

Hi

On Fri, May 05, 2017 at 11:52:49AM +0200, Florian Weimer wrote:
> On 05/05/2017 11:22 AM, Marcus Meissner wrote:
> > On Wed, May 03, 2017 at 05:55:20PM -0700, Seth Arnold wrote:
> > > On Wed, May 03, 2017 at 08:55:23PM +0200, Guido Vranken wrote:
> > > > This vulnerability allows an attacker to allocate any amount of bytes
> > > > (up to 4 gigabytes per attack) on a remote rpcbind host, and the
> > > > memory is never freed unless the process crashes or the administrator
> > > > halts or restarts the rpcbind service.
> > > > [...]
> > > > An extensive write-up can be found here:
> > > > https://guidovranken.wordpress.com/2017/05/03/rpcbomb-remote-rpcbind-denial-of-service-patches/
> > > > 
> > > > Exploit + patches: https://github.com/guidovranken/rpcbomb/
> > > 
> > > Hello Guido, nice find. Have CVE numbers been requested for this issue
> > > yet? Have you investigated if ntirpc is affected too? Much of the code
> > > looks similar:
> > > 
> > > http://sources.debian.net/src/ntirpc/1.4.3-3/src/rpc_generic.c/#L728
> > 
> > We also saw glibc affected.
> > 
> > https://bugzilla.suse.com/show_bug.cgi?id=1037559#c7
> > 
> > That said, your reproducer allocates virtual memory, and on systems with overcommit
> > there is only neglible impact on overall memory pressure.
> > 
> > The rpc service will however likely crash at some point though when there is no virtual
> > address space left for it.
> 
> Thanks, I filed it upstream as well:
> 
> https://sourceware.org/bugzilla/show_bug.cgi?id=21461
> 
> Looks like both xdr_bytes and xdr_string have a similar bug.
> 
> I'd appreciate some guidance on reusing or not reusing CVE IDs here.

A separate CVE should be used for this issue as clarified with MITRE.

It was assigned CVE-2017-8804.

https://sourceware.org/bugzilla/show_bug.cgi?id=21461

Patch posted at
https://sourceware.org/ml/libc-alpha/2017-05/msg00105.html by Florian
Weimer.

Regards,
Salvatore

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