Nth Dimension Security Advisory (NDSA20121010)

Type securityvulns
Reporter Securityvulns
Modified 2012-11-02T00:00:00



Nth Dimension Security Advisory (NDSA20121010) Date: 10th October 2012 Author: Tim Brown <mailto:timb@nth-dimension.org.uk> URL: <http://www.nth-dimension.org.uk/> / <http://www.machine.org.uk/> Product: Konqueror 4.7.3 <http://konqueror.kde.org/> Vendor: KDE <http://www.kde.org/> Risk: Medium


The Konqueror web browser is vulnerable to a number of memory corruption vulnerabilities.

This advisory comes in 4 related parts:

1) The Konqueror web browser is vulnerable to type confusion leading to memory disclosure. The root cause of this is the same as CVE-2010-0046 reported by Chris Rohlf which affected WebKit.

2) The Konqueror web browser is vulnerable to an out of bounds memory access when accessing the canvas. In this case the vulnerability was identified whilst playing with bug #43813 from Google's Chrome repository.

3) The Konqueror web browser is vulnerable to a NULL pointer dereference leading to a crash.

4) The Konqueror web browser is vulnerable to a "use-after-free" class flaw when the context menu is used whilst the document DOM is being changed from within Javascript.

These flaws were identified during an analysis of previously reported vulnerabilities that affected Google's Chrome web browser. It is believed that only vulnerability 1 is/was common to the two code bases.

After discussions with the vendor, the following CVEs were assigned to these vulnerabilities:

1) CVE-2012-4512 2) CVE-2012-4513 3) CVE-2012-4514 4) CVE-2012-4515


Nth Dimension recommends that the vendor supplied patches should be applied:

1) a872c8a969a8bd3706253d6ba24088e4f07f3352 2) 1f8b1b034ccf1713a5d123a4c327290f86d17d53 3) 65464349951e0df9b5d80c2eb3cc7458d54923ae 4) 4f2eb356f1c23444fff2cfe0a7ae10efe303d6d8

Technical Details

1) Chris's blog post (http://em386.blogspot.com/2010/12/webkit-css-type-confusion.html) nicely describes this vulnerability.

It is worth noting that due to an overlap in bugs, our pre-advisory confused CVE-2010-4577 and CVE-2010-0046. Red Hat's bug entry for CVE-2010-4577 references the local() CSS function, whilst their bug entry for CVE-2010-0046 references the format() function (on very similar code paths). In the case of Konqueror, due to a slight reordering in calls, one patch (for CVE-2012-4512) actually fixes both the format() and local() issue.

2) There was a sign-extension in calculating the dimensions of the canvas within scaleLoop , which lead to a miscalculated jump. According to KDE, in the case of 64-bit systems this appeared only to allow a crash to be triggered however on 32-bit systems it could lead to memory disclosure.

The following PoC can trigger the crash on vulnerable versions of Konqueror:

<html> <body> <canvas id="tutorial"></canvas> <script type="text/javascript"> var canvas = document.getElementById("tutorial"); if (canvas.getContext) { var ctx = canvas.getContext("2d"); canvas.width = 111111; } </script> </body> </html>

It is worth noting that unlike vulnerability 2, the code here is not shared between WebKit and Konqueror.

3) Unfortunely I no longer have the stack trace for this crash however it can be triggered on vulnerable versions of Konqueror using the following PoC:

<html> <body> <iframe name="test" src="http://www.google.co.uk"></iframe> <input type=button value="test" onclick="window.open('javascript:alert(document.cookie)','test')" > </body> </html>

4) By accessing the context menu for a given iframe whilst the iframe is being updated by the parent can lead to attempts to access no- onger existing objects. This may lead to a crash, or potentially code execution, depending on the state of the process at the point the no-longer existing object is accessed.

The following PoC can trigger the crash on vulnerable versions of Konqueror:

<html> <body> <script> setInterval(function () { document.body.innerHTML = "<iframe src=about:konqueror></iframe>"; }, 300); </script> </body> </html>


On 27th July 2011, Nth Dimension contacted the KDE security team to report vulnerability 1.

On 7th November 2011, Than Ngo of Red Hat re-reports the vulnerability 1 and Maksim Orlovich from KDE responds confirming that they have received the report and it had been escalated to Maksim Orlovich, a KDE developer working on KHTML to determine the impact. A proposed patch is made available on 13th November 2010.

Nth Dimension continue to examine bugs in WebKit that have been reported to Google and on 1st November 2011 report vulnerability 2. Maksim responds quickly but only to confirm receipt. There are apparently issues in reproducing vulnerability 2. Maksim further responds on the 6th confirming that he now has it working and has identified the root cause.

On 2nd February 2012, Jeff Mitchell of the KDE security team requests details of the patches in order to make the vulnerability details public. Maksim responds that wires were crossed and he was waiting on KDE security team and Nth Dimension. Patch details as above are then supplied,

On 16th February 2012, Nth Dimension report vulnerabilities 3 and 4. The KDE security team propose rolling all 4 bugs into 1 advisory assuming that the final 2 vulnerabilities can quickly be triaged. Maksim responds on the 20th confirming he has them reproduced and offering possible fixes.

Between February and October, Nth Dimension hear no further updates despite chasing the KDE security team in June.

Nth Dimension proceed to post limited details to oss-security on 10th October 2012.

Following this, representatives from Red Hat and KDE liased with Nth Dimension to resolve the oustanding issues. Further patches were supplied by David Faure of KDE and tested by Jan Lieskovskyi and other members of the Red Hat security team. On 26th October 2012 an embargo was agreed to allow Nth Dimension and Red Hat further time to review the supplied patch for vulnerability 4. KDE will commit the proposed patch allowing disclosure on, or shortly after 29th October 2012.


As of the 30th October 2012, the state of the vulnerabilities is believed to be as follows. Patches have been applied to Konqueror which resolve all vulnerabilities.


Nth Dimension would like to thank Jeff Mitchell, Maksim Orlovich and David Faure of KDE as well as Jan Lieskovskyi, Vincent Danen, Kurt Seifried of the Red Hat security team for the way they worked to resolve the issues. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux)

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