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Date: Fri, 3 Oct 2014 15:26:09 +0400
From: Solar Designer <>
Subject: Re: sysklogd vulnerability (CVE-2014-3634)

On Fri, Oct 03, 2014 at 11:24:43AM +0000, mancha wrote:
> On Fri, Oct 03, 2014 at 09:12:28AM +0000, mancha wrote:
> > In sysklogd's syslogd, invalid priority values between 192 and 1023
> > (directly or arrived at via overflow wraparound) can propagate through
> > code causing out-of-bounds access to the f_pmask array within the
> > 'filed' structure by up to 104 bytes past its end. Though most likely
> > insufficient to reach unallocated memory because there are around 544
> > bytes past f_pmask in 'filed' (mod packing and other differences),
> > incorrect access of fields at higher positions of the 'filed'
> > structure definition can cause unexpected behavior including message
> > mis-classification, forwarding issues, message loss, or other.
> To expand on the above, because the out-of-bounds access is limited to
> the filed structure, the effect on message handling, etc. appears
> limited to the would-be attacker's own message. Unlike the more serious
> impact seen in rsyslog, my limited testing and code review suggests the
> flaw, while there, has no real security impact. Nevertheless, my patch
> fixes the handling of malformed PRI parts.

What about the DoS impact claimed here, though? -

 A segfault seems possible in sysklogd if a negative facility value (due to
 integer overrun in facility parsing) is used. This could be used to
 carry out a remote DoS.

If this can be used to crash syslogd, it's "real security impact", even
if rather limited.

Have you tried triggering this condition (getting syslogd to crash)?


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