MS02-054: Unchecked Buffer in File Decompression Functions Could Lead


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Title: Unchecked Buffer in File Decompression Functions Could

Lead to Code Execution (Q329048)

Date: 02 October 2002

Software: Microsoft Windows 98 with Plus! Pack, Windows Me,

or Windows XP

Impact: Two vulnerabilities, the most serious of which could

run code of attacker?s choice

Max Risk: Moderate

Bulletin: MS02-054

Microsoft encourages customers to review the Security Bulletin at:

http://www.microsoft.com/technet/security/...in/MS02-054.asp

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Issue:

======

Zipped files (files having a .zip extension) provide a means to

store information in a way that uses less space on a hard disk. This is accomplished by compressing the files that are put into in the zipped file. On Windows 98 with Plus! Pack, Windows Me and Windows XP, the Compressed Folders feature allows zipped files to be treated as folders. The Compressed Folders feature can be used to create, add files to, and extract files from zipped files.

Two vulnerabilities exist in the Compressed Folders function:

- An unchecked buffer exists in the programs that handles the

decompressing of files from a zipped file. A security

vulnerability results because attempts to open a file with

a specially malformed filename contained in a zipped file could

possibly result in Windows Explorer failing, or in code of the

attacker?s choice being run.

- The decompression function could place a file in a directory

that was not the same as, or a child of, the target directory

specified by the user as where the decompressed zip files should

be placed. This could allow an attacker to put a file in a known

location on the users system, such as placing a program in a

startup directory

Mitigating Factors:

====================

- The vulnerabilities could not be exploited without user

intervention. The attacker would need to entice the user to

receive, store, and open the zipped file provided by the

attacker.

- The vulnerabilities could not be exploited remotely. An attacker

would need to lure a user into receiving the zipped file onto

the user?s machine. Best practices suggest users not accept

e-mail attachments from people who are not trusted, and not to

download files from untrusted Internet sites.

- On Windows 98 and Windows Me, the Compressed Folders feature is

not installed by default. Users who had not installed this

feature would not be vulnerable.

Risk Rating:

============

- Internet systems: Low

- Intranet systems: Low

- Client systems: Moderate

Patch Availability:

===================

- A patch is available to fix this vulnerability. Please read the

Security Bulletin at

http://www.microsoft.com/technet/security/...in/ms02-054.asp

for information on obtaining this patch.

Acknowledgment:

===============

- Joe Testa of Rapid7, Inc. (http://www.rapid7.com/) for reporting

the Unchecked Buffer in Zipped File Handling vulnerability.

- zen-parse for reporting the Incorrect Target Path for Zipped

File Decompression vulnerability.

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Source: Microsoft Email

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