Bug#560946: CVE-2009-3560 and CVE-2009-3720 denial-of-services

Michael Gilbert michael.s.gilbert at gmail.com
Mon Dec 14 16:31:18 UTC 2009


retitle 560946 xulrunner: embeds expat
severity 560946 important
thanks

On Mon, 14 Dec 2009 09:15:12 +0100, Mike Hommey wrote:
> On Sat, Dec 12, 2009 at 10:56:59PM -0500, Michael Gilbert wrote:
> > package: xulrunner
> > severity: serious
> > tags: security
> > 
> > Hi,
> > 
> > The following CVE (Common Vulnerabilities & Exposures) ids were
> > published for expat.  I have determined that this package embeds a
> > vulnerable copy of xmlparse.c and xmltok_impl.c.  However, since this is
> > a mass bug filing (due to so many packages embedding expat), I have
> > not had time to determine whether the vulnerable code is actually
> > present in any of the binary packages derived from this source package.
> > Please determine whether this is the case. If the binary packages are
> > not affected, please feel free to close the bug with a message
> > containing the details of what you did to check.
> > 
> > CVE-2009-3560[0]:
> > | The big2_toUtf8 function in lib/xmltok.c in libexpat in Expat 2.0.1,
> > | as used in the XML-Twig module for Perl, allows context-dependent
> > | attackers to cause a denial of service (application crash) via an XML
> > | document with malformed UTF-8 sequences that trigger a buffer
> > | over-read, related to the doProlog function in lib/xmlparse.c, a
> > | different vulnerability than CVE-2009-2625 and CVE-2009-3720.
>  
> From what I understand from the vulnerability, the an specially crafted
> big5 encoded document can trigger a bad conversion to utf-8 which in
> turn can trigger this bug, due to the malformed utf-8.
> 
> > CVE-2009-3720[1]:
> > | The updatePosition function in lib/xmltok_impl.c in libexpat in Expat
> > | 2.0.1, as used in Python, PyXML, w3c-libwww, and other software,
> > | allows context-dependent attackers to cause a denial of service
> > | (application crash) via an XML document with crafted UTF-8 sequences
> > | that trigger a buffer over-read, a different vulnerability than
> > | CVE-2009-2625.
> 
> This one is about a buffer overrun from malformed utf-8 at the end of
> the buffer.
> 
> AFAIK, none of these bugs should be affecting the mozilla code base, as
> it is doing its own utf-8 conversions and sanitizes it well before it
> comes to expat. 

sounds reasonable to me.  so to harden for future issues, i would still
recommend updating xulrunner to use the system expat.  thanks.

mike





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