Qualys Blog

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Keeping up with DLL hijacking

A week has passed since Microsoft published security advisory KB2269637 that details the technology underlying the DLL hijacking vulnerabilities. Since then security researchers have looked at Windows applications from 3rd parties and from Microsoft itself and have identified many vulnerable programs Last week HD Moore from Rapid7 published an even better version of his DLL Hijacking finding tool that is in use by many of the researchers. Microsoft gave a very illustrative example on how a vulnerable application could be attacked on their SRD blog just this week.

We recommend installing the Microsoft Hotfix downloadable from KB2264107 and creating the CWDIllegalInDllSearch registry key, which instructs Windows to exclude the current working directory from the DLL loadpath when an application is started from network or WebDAV locations. In addition IT admins should keep an eye on the excellent list on vulnerable applications and their fix status that is being maintained by Secunia.

In Qualysguard we have introduced 2 new QIDs that are designed to help the IT admin to manage the installation of this Hotfix:

  • QID 118423 – Microsoft Windows DLL Search Order Design Error Vulnerability (KB2269637)
    This detection indicates that the machine does not have the Hotfix installed
  • QID 90634 – Hotfix KB2264107 (DLL hijacking) is Installed
    This detection indicates that the machine has the Hotfix installed and will contain the setting for registry key CWDIllegalInDllSearch in the result section

Microsoft provides advisory for DLL hijacking exploits

Microsoft has just published security advisory KB2269637 that provides IT admins with the information and tools to deal with DLL hijacking. DLL hijacking attacks are targeted at Windows applications (3rd part and Microsoft) that have not followed recommended security practices and can be tricked to load DLLs from locations that are owned by the attacker. The attacker provided DLL is then used to take control of the target machine.

According to security research by Taeho Kwon and Zhendong Su from UC Davis, ACROS Security and HD Moore from Rapid7, it is straightforward to find applications that do not follow these best practices. Two weeks iTunes was patched for an occurrence of "binary planting" and Simon Raner of ACROS Security was credited.

The underlying idea of the attack is older (some discussion of the underlying issue is here from 2000) and not limited to Windows. Over time fixes and workarounds have been implemented, but a new attack vector using network shares and WebDAV increases the usability of the attack. With the available documentation and tools it is now easy to find vulnerable applications and craft exploits.

We recommend installing the hotfix in KB2264107 and setting the registry to not allow loading of binaries via network shares and WebDAV (setting 2) as soon as possible.


Adobe Patches Reader/Acrobat on Windows, Mac and Unix

Today Adobe published an out-of-band update APSB10-17 for a 0-day vulnerability published during Charlie Miller’s BlackHat talk.

The vulnerability is critical and can be used to take control of the targeted computer and should be addressed as soon as possible.

Adobe credits Tavis Ormandy for the discovery of the vulnerability. It seems that Tavis reported the vulnerability to Adobe before Charlie’s Black Hat presentation. This is an example that illustrates an effect that security researchers have long tried to call attention to: it is possible and seems to happen every once in a while that vulnerabilities are discovered independently, both by security researchers and/or malware writers. Tipping Point’s ZDI initiative would be in a position to publish statistics on how often they have such an overlap.

The update also includes the update to Flash (Adobe Reader brings its own embedded Flash version) released last week – APSB10-016 and further improves the handling of vulnerability CVE-2010-1240, which was first addressed in June in APSB10-015.

Patch Tuesday Bottomline – August 2010

A busy week – in addition to Microsoft August’s Patch Tuesday which delivers a record setting 15 bulletins covering 35 vulnerabilities, Adobe has just released a Flash update and will be releasing a patch for a Adobe Reader 0-day vulnerability published a few weeks ago at Black Hat security conference.To help with this challenging patch workload, we have ranked the Microsoft bulletins into three distinct groups of updates, which can be addressed on different schedules.

IT admins should first tackle the updates that represent the biggest attack potential: end-users and internet browsing are at the subject of six bulletins, all of them of critical severity and four of them with an exploitability rating of "1", indicating that working exploits are expected within 30 days. MS10-053 has six direct fixes for Internet Explorer, while the ZDI submitted MS10-055 and MS10-052 address issues in media-plugins: MS10-055 for the Cinepak codec and MS10-052 for the MP3 file format. MS10-060 patches a critical .NET framework issue that can be exploited through web browsing/Silverlight and MS10-051 addresses a vulnerability in the Internet Explorer MSXML ActiveX component. MS10-049 deals with a client side vulnerability of the HTTPS protocol that can be triggered by a malicious HTTPS site. This and the previous MSXML ActiveX component are the bulletins in the group that are rated "2" on the exploitability scale (= harder to exploit). All of these updates should be applied as soon as possible.

A second group of updates has its focus on file format vulnerabilities. The most critical is MS10-056, a vulnerability in the RTF format in Microsoft Word 2007 and older. An attacker can craft a malicious file that triggers a remote code execution when opened by Word on the target computer. Users of Outlook 2007 installations need to pay special attention, since the preview pane in Outlook is configured by default to use Word to render the RTF format. This makes Outlook 2007 susceptible to an attack that does not even require the opening of the e-mail. Apply this update as quickly as possible. MS10-057 and MS10-050 provide fixes for Excel 2003 and earlier and Windows Movie Maker (a default component in Windows XP) file format vulnerabilities. Both have an exploitability rating of "1" and should be addressed as soon as possible.

MS10-058 deals with an interesting vulnerability. It is a located in the new TCP/IP stack for IPv6 under Vista, Windows 7 and 2008R2. While we believe that currently very few publicly facing network infrastructures have IPv6 enabled, this bulletin is important for them, because it is remotely attackable and few mitigations exist. It is a reminder that new OS components and applications are apt to introduce new attack vectors into networks. MS10-054 is a vulnerability in the SMB protocol; it requires read access to a share as well as attacker-controlled data on the target machine. The exploit here will most likely manifest itself as a local escalation of privilege attack.

The remainder of the August updates all address local flaws of the Windows Operating system family and are rated important as the attacker needs to be present on the target system to make use of them. MS10-047 is a Windows Kernel flaw, MS10-048 a flaw in the win32k.sys driver and MS10-059 fixes a problem in the tracing component of Windows.

Last week Microsoft released a bulletin for the 0-day flaw using the LNK filetype. If you have not done so yet, apply MS10-046 together with the first group of patches as desktop systems are at the highest risk of attack using the LNK vulnerability.


Adobe Prenotification for August 2010

Adobe announced that they will publish an out-of-band update APSB10-17 for a 0-day vulnerability published during Charlie Miller’s BlackHat talk.

Charlie Miller’s BlackHat paper is a result of a collaboration with Prof. Dawn Song from UC Berkeley and a continuation of his fuzzing efforts first revealed at the CanSecWest conference. At the time the tools he used were CrashWrangler and !exploitable, but it seems that BitBlaze, the tool from Prof. Song’s research group provides much better insight into exploitable application crashes.

Patch Tuesday – Preview for August 2010

This August is bringing a record setting number of updates from Microsoft. In addition to last week’s LNK update, there will be another 14 bulletins addressing 34 vulnerabilities, that IT admins will have to take care of in the weeks after Patch Tuesday. Including the LNK update,9 bulletins have a rating of critical and affect all version of the Windows OS, Internet Explorer, Silverlight and Microsoft Office.

Windows 7 and 2008 R2 have a smaller number of critical vulnerabilities than Windows XP and 2003 in function of their improved security architecture, but are still affected by 2 critical vulnerabilities each.

Internet Explorer, Office and Silverlight updates apply across the board on all Windows versions. They are a examples of the this increasingly used type of flaw, where attackers and malware go through the installed applications rather than through the core operating system.

Windows XP SP2 users do not have any patches supplied to them, even though the 5 critical vulnerabilities for XP SP3 most likely apply to their discontinued version of the OS as well. Windows XP SP2 users should upgrade to SP3 as quickly as possible.

MS10-046 fixes 0-day LNK vulnerability out of band

Microsoft released an update today that addresses the LNK vulnerability. The update is rated as critical and applies to all currently supported Windows Operating systems.

We recommend applying the update as quickly as possible. Attacks using this 0-day vulnerability have been increasing.

The recently discontinued Windows 2000 and Windows XP SP2 are not covered by the patch. Users of these Windows 2000 and XP SP2 need to work on an upgrade strategy for these operating systems, as over time without patch support they will become increasingly susceptible to attacks from malware