Vulnerability in Microsoft Internet Explorer - Update

Number: AL13-003 - Update
Date: 20 Septembre 2013

Purpose - Update

The purpose of this Alert is to raise awareness that Internet Storm Centre is reporting an increase in evidence of exploits in the wild for a vulnerability in Microsoft Internet Explorer (IE) which could allow remote code execution. (2887505). Internet Storm Centre is also reporting "There is some indication that a weaponized exploit may be in broader circulation now, so expect this to ramp up quickly." Internet Storm Centre has moved their InfoCon up to Yellow.

Assessment - Update

CCIRC is aware that Microsoft is reporting a vulnerability affecting IE 8 and IE 9. This vulnerability is a remote code execution vulnerability and Microsoft is reporting that it is being used in targeted attacks.

CVE Reference: CVE-2013-3893

Microsoft advises that applying the Microsoft Fix it solution, "CVE-2013-3893 MSHTML Shim Workaround", prevents the exploitation of this issue in most cases. Internet Storm Centre notes that "the Fix It seems to only help 32-bit versions of browsers. That said the vulnerability affects all versions of Internet Explorer except in instances of Windows Server 2008 and 2012 Core installations. Emerging Threats does have Snort signatures "2017477 – ET WEB_CLIENT CVE-2013-3893 Possible IE Memory Corruption Vulnerability with HXDS ASLR Bypass (web_client.rules)" available for this issue: . Expect Rapid 7 to likely release Metasploit bits in the near term. We'll update here as we see more on this vulnerability emerge."

Suggested Action

CCIRC recommends that system administrators identify their affected assets and potential interdependencies with their organization's critical services and follow their patch management process accordingly.


Note to Readers

In support of Public Safety's mission to build a safe and resilient Canada, CCIRC's mandate is to help ensure the security and resilience of the vital non-federal government cyber systems that underpin Canada's national security, public safety and economic prosperity. As Canada's computer security incident response team, CCIRC is Canada's national coordination centre for the prevention and mitigation of, preparedness for, response to, and recovery from cyber incidents on non-federal government systems. It does this by providing authoritative advice and support, and coordinating information sharing and incident response.

Please note, CCIRC PGP key has recently been updated.

For general information, please contact Public Safety Canada's Public Affairs division at:

Telephone: 613-944-4875 or 1-800-830-3118
Fax: 613-998-9589

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