Vulnerability Note VU#648406

Apple Mac OS X AppleFileServer fails to properly handle certain authentication requests

Overview

There is a buffer overflow vulnerability in the way Apple's AppleFileServer handles certain authentication requests. This vulnerability could allow an unauthenticated, remote attacker to execute arbitrary code.

I. Description

The AppleFileServer provides Apple Filing Protocol (AFP) services for clients and servers. This protocol allows users to share files over the network. By default the AFP service is not enabled. There is a buffer overflow vulnerability in the way the AppleFileServer handles certain authentication requests. By supplying a specially crafted PathName argument during authentication, an unauthenticated, remote attacker could execute arbitrary code.

According to the @stake advisory:

There is a pre-authentication, remotely exploitable stack buffer overflow that allows an attacker to obtain administrative privileges. The overflow occurs when parsing the PathName argument from LoginExt packet requesting authentication using the Cleartext Password User Authentication Method (UAM). The PathName argument is encoded as one-byte specifying the string type, two-bytes specifying the string length, and finally the string itself. A string of type AFPName (0x3) that is longer than the length declared in the packet will overflow the fixed-size stack buffer.

II. Impact

An unauthenticated, remote attacker could execute arbitrary code.

III. Solution

Apply Patch

Apple has issued an advisory to address this issue. For further details, please see the Apple Security Advisory (Security Update 2004-05-03).

Disable AppleFileServer

Until a patch can be applied, you may wish to disable the AppleFileServer.

Systems Affected

Vendor	Status	Date Notified	Date Updated
Apple Computer Inc.	Vulnerable	7-May-2004

References

http://www.atstake.com/research/advisories/2004/a050304-1.txt
http://docs.info.apple.com/article.html?artnum=61798
http://secunia.com/advisories/11539/
http://www.securiteam.com/securitynews/5QP0115CUO.html
http://www.securitytracker.com/alerts/2004/May/1010039.html2

Credit

This vulnerability was reported by Dave G. of @stake.

This document was written by Damon Morda based on information in the @stake advisory.

Other Information

Date Public:	2004-05-03
Date First Published:	2004-05-07
Date Last Updated:	2004-05-07
CERT Advisory:
CVE-ID(s):	CAN-2004-0430
NVD-ID(s):	CAN-2004-0430
US-CERT Technical Alerts:
Metric:	27.42
Document Revision:	24

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