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Windows: creating unreachable files
Synthesis of the vulnerability
A local attacker can create a file on system which is not detected or cleaned by some checking tools, such as antivirus.
Impacted products: Avast AV, F-PROT AV, AVG AntiVirus, Kaspersky AV, Windows 2000, Windows NT, Windows XP.
Severity of this bulletin: 1/4.
Consequences of an intrusion: disguisement.
Hacker's origin: user shell.
Creation date: 11/05/2006.
Références of this threat: BID-17934, VIGILANCE-VUL-5835.
Description of the vulnerability
The RtlDosPathNameToNtPathName_U() function converts a Unicode MS-DOS pathname to NT pathname. It uses:
- RtlGetFullPathName_Ustr(), if path has to be converted
- RtlpWin32NTNameToNtPathName_U(), if path is already in NT format
However, both functions differently manage spaces located at end of paths:
- the first one suppress them
- the second one keeps them
Thus, the "\\?\C:\test " NT filename cannot be accessed using "C:\test " MS-DOS path.
For example, antivirus using the MS-DOS filename format cannot detect or disinfect viruses located in these files.
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