Apple Computer Inc. late Tuesday shipped a massive Mac OS X update to correct security flaws in several Internet-facing components, including multiple code execution bugs in the Safari Web browser.

In all, Apple's Security Update 2005-009 addresses 13 vulnerabilities affecting Mac OS X (both client and server editions).

Security alerts aggregator Secunia Inc. rated the update as "highly critical" and warned that malicious hackers could exploit the flaws to launch security bypass, cross-site scripting, spoofing, data manipulation, information exposure, denial-of-service and system access attacks.

Two of the four Safari patches can lead to arbitrary code execution, Apple acknowledged in an alert.

The first is an error in the way the browser processes regular expression.

"The JavaScript engine in Safari uses a version of the PCRE library that is vulnerable to a potentially exploitable heap overflow," Apple said, warning that it could lead to the execution of harmful code.

The update addresses the issue by providing a new version of the JavaScript engine that incorporates more robust input validation.

Safari users visiting malicious Web sites with WebKit-based applications are also at risk of code execution attacks because of a heap overflow in WebKit, Apple said. The overflow may be triggered by content downloaded from malicious Web sites in applications that use WebKit.

A third bug in Safari may cause the browser to download files outside of the designated download directory. When files are downloaded in Safari, Apple said, they are normally placed in the location specified as the download directory.

However, if a Web site suggests an overlong filename for a download, it is possible for Safari to create this file in other locations.

"Although the filename and location of the downloaded file content cannot be directly specified by remote servers, this may still lead to downloading content into locations accessible to other users," the patch page reads.

The browser was also modified to fix an issue that caused JavaScript dialog boxes to be misleading.

The bug meant that JavaScript dialog boxes do not indicate the Web site that created them, setting up a situation were Safari users were misled into unintentionally disclosing information to a Web site.

The Mac OS X update also addresses a serious error in the handling of HTTP headers in the Apache 2 Web server. This bug can be exploited by malicious people to conduct HTTP-request smuggling attacks when Apache is used in conjunction with certain proxy servers, caching servers or Web application firewalls.

Also fixed is an error in the Apache Web server's "modest" module that can be exploited to bypass certain security restrictions.

Other components fixed in the update are Core Foundation, CoreTypes, curl, iodbcadmin, OpenSSL, sudo and syslog.

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