Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Thu, 20 Nov 2008 03:16:36 +0300
From: Eygene Ryabinkin <>
Cc: "Steven M. Christey" <>
Subject: Re: CVE request: CUPS DoS via RSS subscriptions

Josh, Mike, *, good day.

Wed, Nov 19, 2008 at 03:14:43PM -0500, Josh Bressers wrote:
> So from looking at cups 1.3.7 on Fedora 8, here is what I see:
> (gdb) bt
> #0  create_subscription (con=0xb88975c0, uri=0xb889ae00) at ipp.c:5858
> #1  0xb7facba7 in cupsdProcessIPPRequest (con=0xb88975c0) at ipp.c:615
> #2  0xb7f88bfc in cupsdReadClient (con=0xb88975c0) at client.c:2253
> #3  0xb7fc0606 in cupsdDoSelect (timeout=1) at select.c:537
> #4  0xb7f98710 in main (argc=1, argv=0xbfdd6194) at main.c:817
> (gdb) list
> 5853        else if (printer)
> 5854          cupsdLogMessage(CUPSD_LOG_DEBUG,
> 5855                          "Added subscription %d for printer \"%s\"",
> 5856                          sub->id, printer->name);
> 5857        else
> 5858          cupsdLogMessage(CUPSD_LOG_DEBUG, "Added subscription %d for server",
> 5859                          sub->id);
> 5860
> 5861        sub->interval = interval;
> 5862        sub->lease    = lease;
> (gdb) print sub
> $1 = (cupsd_subscription_t *) 0x0
> It would appear to be a NULL pointer dereference.  It seems that this call a
> few lines above the snippet shown above:
>  sub = cupsdAddSubscription(mask, printer, job, recipient, 0);
> will return NULL when the hardcoded value of 100 subscriptions is hit.

Not really hardcoded -- it is settable with the 'MaxSubscriptions'
directive.  I had just reproduced the bug with CUPS 1.3.9 at FreeBSD.
MaxSubscriptions was set to 3 to ease the PoC.  Just repeated
invocations of 'lpr -m <somefile>' were crashing cups daemon

The attached patch fixes the things for me, but perhaps it needs
some more polishing.  Will try to take a fresh look at this tomorrow.

Mike, please, take a look at this!

View attachment "a" of type "text/plain" (1548 bytes)

Powered by blists - more mailing lists

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.