ZDI-11-249: (Pwn2Own) Microsoft Internet Explorer Protected Mode Bypass Vulnerability
August 9, 2011
-- CVSS: 6.4, (AV:N/AC:L/Au:N/C:P/I:P/A:N)
-- Affected Vendors: Microsoft
-- Affected Products: Microsoft Internet Explorer
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-- Vulnerability Details: This vulnerability allows remote attackers to escape Protected Mode on vulnerable installations of Internet Explorer.
Internet Explorer Protected Mode consists of a Medium Integrity and a Low Integrity process. The Low Integrity process is only allowed to write to special Low Integrity locations. File written there are marked as Low Integrity files. When a new Internet Explorer process is launched it checks the Integrity of the file it is launched against. If the file is a Low Integrity file it will run the process in Low Integrity Mode. It is however possible to give the file an even lower permission: Untrusted, since this does not match the check for 'Low Integrity' the Internet Explorer will run in Medium Integrity instead of Low Integrity. This can be abused in an exploit to bypass the Protected Mode design and thus allow an attacker to escalate their privileges.
-- Vendor Response: Microsoft has issued an update to correct this vulnerability. More details can be found at: http://www.microsoft.com/technet/security/bulletin/MS11-057.mspx
-- Disclosure Timeline: 2011-03-09 - Vulnerability reported to vendor 2011-08-09 - Coordinated public release of advisory
-- Credit: This vulnerability was discovered by: * Stephen Fewer of Harmony Security (www.harmonysecurity.com)
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