The update fixes the following security issues in Mac OS X:

AirPort
A heap buffer overflow exists in the AirPort wireless driver's handling of probe response frames. An attacker in local proximity may be able to trigger the overflow by sending maliciously-crafted information elements in probe responses. This issue affects eMac, iBook, iMac, PowerBook G3, PowerBook G4, and Power Mac G4 systems equipped with an original AirPort card. This issue does not affect systems with the AirPort Extreme card. This update addresses the issue by performing additional validation of probe response frames. Apple offers credit to H D Moore of Metasploit for reporting this issue.

ATS
The Apple Type Services server insecurely creates error log files. As a result, a malicious local user may be able to overwrite or create files with system privileges. This update addresses the issue by creating error logs securely.
Multiple buffer overflows were discovered in Apple Type Services server. By sending a maliciously-crafted service request, a local user may trigger these overflows. This may lead to a crash or arbitrary code execution with system privileges. This update addresses the issue by performing additional validation on service requests. This issue does not affect systems prior to Mac OS X 10.4.
The Apple Type Services server contains a stack buffer overflow in font processing. By carefully crafting a corrupt font file, an attacker can trigger the buffer overflow which may lead to a crash or arbitrary code execution with system privileges. Font files are processed when opened or previewed in Finder. This update addresses the issue by performing additional validation of font files.

CFNetwork
By enticing a user to access a maliciously-crafted FTP URI, an attacker can cause the user's FTP client to issue arbitrary FTP commands to any accessible FTP server, using the credentials of the victim. This issue may also facilitate attacks of other line oriented protocols, such as SMTP. This update addresses the issue by performing additional validation of URIs.

ClamAV
ClamAV is updated to version 0.88.5 to address several security issues. ClamAV was introduced in Mac OS X Server 10.4 for email scanning. The most severe of these issues could lead to arbitrary code execution with the privileges of ClamAV.

Finder
A heap buffer overflow may be triggered when the Finder is used to browse a directory containing a corrupt ".DS_Store" file. By enticing a user to browse a directory containing a maliciously-crafted ".DS_Store" file, an attacker may be able to trigger the overflow. This could lead to an application crash or arbitrary code execution with the privileges of the user running Finder. ".DS_Store" files may be included in archives, on disk images, and on network file systems. This update addresses the issue by performing additional validation of ".DS_Store" files.

ftpd
When attempting to authenticate a valid user, the FTP server may crash during a failed login attempt. The crash does not occur when attempting to authenticate unknown users. This behavior can be used to determine if an account name is valid. This issue is addressed by resolving the crash condition. FTP Access is not enabled by default. Mac OS X Server 10.3.9, Mac OS X 10.4, Mac OS X Server 10.4, and later systems are not affected. Apple offers credit to Benjamin Williams of the University of Canterbury for reporting this issue.

gnuzip
By carefully crafting a malicious compressed file, an attacker may be able to trigger any of several vulnerabilities in gunzip when the file is processed. The most severe of these issues could lead to an application crash or arbitrary code execution. Many applications use the gunzip command for decompression, including command-line tools such as tar and services such as Mail Server. This update addresses the issue by performing additional validation of compressed files. Apple offers credit to Tavis Ormandy of the Google Security Team for reporting this issue.

Installer
Admin users are normally required to authenticate before executing commands with system privileges. However, the Installer allows system privileges to be used by Admin users when installing certain packages without requiring authentication. This update addresses the issue by requiring authentication before installing software with system privileges.

OpenSSL
OpenSSL is updated to version 0.9.7l to address several critical vulnerabilities. The most severe of these vulnerabilities may lead to impersonation of services using SSL or TLS, or to arbitrary code execution.

perl
An integer overflow exists in Perl's format string functionality. This integer overflow may lead to arbitrary code execution in Perl applications which use format strings unsafely. This update addresses the issue by performing additional validation of uses of format strings.

PHP
PHP is updated to version 4.4.4 to address several security issues in the Apache module and scripting environment. Applications using affected APIs may be vulnerable. The most severe of the vulnerabilities may lead to arbitrary code execution.
Buffer overflows exist in the htmlentities() and htmlspecialchars() functions. These buffer overflows may lead to arbitrary code execution in applications using the affected APIs. This update addresses the issue by performing additional validation of input to the affected APIs.

PPP
When PPPoE is enabled, an attacker on the local network may be able to trigger a buffer overflow. This could lead to a system crash or arbitrary code execution with system privileges. This update addresses the issue by performing better validation on PPPoE traffic. PPPoE is not enabled by default. Apple offers credit to the Mu Security research team for reporting this issue.

Samba
The list of active connections tracked by Windows Sharing may grow unbounded. An attacker may be able to create many connections, leading to memory exhaustion and a denial of service. This update addresses the issue by limiting the number of active connections. Windows Sharing is not enabled by default.

Security Framework
Secure Transport provides the ability to encrypt and authenticate data using several ciphers. When a connection is made, the best mutually-supported cipher should be used. Due to the order they are evaluated, it is possible for Secure Transport to use a cipher that provides no encryption or authentication when better ciphers are available. This update addresses the issue by giving priority to better ciphers. Applications using Secure Transport through CFNetwork, such as Safari, are not affected by this issue on systems with Security Update 2006-006 or later. This issue does not affect systems using Mac OS X 10.4.8 and later. Apple offers credit to Eric Cronin of gizmolabs for reporting this issue.
It is possible to create an X.509 certificate containing a public key that could consume a significant amount of system resources during signature verification. An attacker may cause a system to process such a certificate, leading to a denial of service. This issue does not affect systems prior to Mac OS X 10.4. Apple offers credit to Dr. Stephen N. Henson of Open Network Security for reporting this issue, and to NISCC for coordinating.
On systems that are configured to use an HTTP proxy, the Online Certificate Status Protocol (OCSP) service is unable to retrieve certificate revocation lists. This update addresses this issue by using the system proxy settings in ocpsd. This issue does not affect systems prior to Mac OS X 10.4. Apple offers credit to Timothy J. Miller of the MITRE Corporation for reporting this issue.
The revocation list from an issuing authority may not be consulted for certain leaf certificates. This update addresses the issue through improved handling of the certificate revocation list. This issue does not affect Mac OS X 10.4.7 and later systems. Apple offers credit to Jose Nazario of Arbor Networks for reporting this issue.

VPN
Under certain circumstances, the VPN server may execute commands without properly cleaning the environment. This may allow a malicious local user to create files or execute commands with system privileges. This update addresses the issue by ignoring the user's environment when executing commands.

WebKit
A maliciously-crafted HTML document could cause a previously deallocated object to be accessed. This may lead to an application crash or arbitrary code execution. This update addresses the issue by properly handling such documents. Apple offers credit to Tom Ferris of Security-Protocols for reporting this issue.