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Date: Tue, 3 Feb 2015 13:15:17 +0200
From: Constantine Shulyupin <>
To: Florian Weimer <>
Cc: oss-security <>
Subject: Re: workaround for GHOST glibc vulnerability CVE-2015-0235

Added static, thank.

You are right, gethostbyname is vulnerable too, but less.
gethostbyname is implemented in
It allocates buffer from heap, not stack, which is less danger.

Actually the bug is in __nss_hostname_digits_dots @
Is it much more complex and dangerous to overload
__nss_hostname_digits_dots. Better upgrade to newer glibc.


On Tue, Feb 3, 2015 at 12:30 PM, Florian Weimer <> wrote:

> On 02/02/2015 03:52 PM, Constantine Shulyupin wrote:
> > CVE-2015-0235-workaround is a shared library wrapper with additional
> checks
> > for the vulnerable functions gethostbyname2_r and gethostbyname_r .
> >
> > The proper solution for CVE-2015-0235 is to upgrade glibc to at least
> > glibc-2.18.
> >
> > In some cases, an immediate glibc upgrade is not possible, for example in
> > custom production embedded systems, because such an upgrade requires a
> > validation of the whole system.
> >
> > In such cases, this workaround provides a hot fix solution, which is
> easier
> > to validate.
> >
> > Source code:
> You should make all symbols static.  With the current code, you risk
> symbol collisions.
> Why don't you hook gethostbyname?  I'm not sure if gethosybyname is
> implement in terms of gethostbyname_r.  (The call stacks I have suggest
> it isn't.)
> --
> Florian Weimer / Red Hat Product Security

Constantine Shulyupin
Embedded Linux Systems
and Device Drivers

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