If you want all the gory details on how each of these vulnerabilities are exploitable, Apple has that information published here.
When you think about it, it's shocking how backward Apple really is when it comes to how it communicates security issues to its customers. Must be the lack of enterprise installed base: there's no clear delineation of criticality; these are released ad hoc (Microsoft, Oracle, and others abolished that practice years ago to help their business customers); and the descriptions are a bit obscure.
Nonetheless, you can see that there are a few biggies. The key words to look for in lists like this are phrases like privilege, arbitrary code execution, and remote. While flaws that lead to a denial-of-service can be problematic, they don't always lead to a compromised PC -- as arbitrary code often does.
Here are all of the security flaws, 14 out of the 36 total bugs fixed. The list is from Apple. I've cut it down to CVE-ID, affected software, and impact. The CVE-ID is the Common Vulnerabilities and Exposures identifier, the CVE is basically a list, or dictionary, that provides a common name for publicly known vulnerabilities.
The flaws that look especially troublesome, to me, include CVE-2008-4217, CVE-2008-3623, CVE-2008-3170, CVE-2008-4220, CVE-2008-4221, and CVE-2008-1391. That's at least six of the 14 security flaws. No small ratio of serious vulnerabilities.
ATS
CVE-ID: CVE-2008-4236
Available for: Mac OS X v10.5 through v10.5.5, Mac OS X Server v10.5 through v10.5.5
Impact: Viewing or downloading a PDF file containing a maliciously crafted embedded font may lead to a denial of service
BOM
CVE-ID: CVE-2008-4217
Available for: Mac OS X v10.4.11, Mac OS X Server v10.4.11, Mac OS X v10.5 through v10.5.5, Mac OS X Server v10.5 through v10.5.5
Impact: Downloading or viewing a maliciously crafted CPIO archive may lead to arbitrary code execution or unexpected application termination
CoreGraphics
CVE-ID: CVE-2008-3623
Available for: Mac OS X v10.4.11, Mac OS X Server v10.4.11, Mac OS X v10.5 through v10.5.5, Mac OS X Server v10.5 through v10.5.5
Impact: Viewing a maliciously crafted image may lead to an unexpected application termination or arbitrary code execution
CoreServices
CVE-ID: CVE-2008-3170
Available for: Mac OS X v10.4.11, Mac OS X Server v10.4.11, Mac OS X v10.5 through v10.5.5, Mac OS X Server v10.5 through v10.5.5
Impact: Visiting a maliciously crafted Web site may lead to the disclosure of user credentials
CoreTypes
CVE-ID: CVE-2008-4234
Available for: Mac OS X v10.5 through v10.5.5, Mac OS X Server v10.5 through v10.5.5
Impact: Attempting to launch unsafe downloaded content may not lead to a warning
Flash Player Plug-in
CVE-ID: CVE-2008-4818, CVE-2008-4819, CVE-2008-4820, CVE-2008-4821, CVE-2008-4822, CVE-2008-4823, CVE-2008-4824
Available for: Mac OS X v10.4.11, Mac OS X Server v10.4.11, Mac OS X v10.5 through v10.5.5, Mac OS X Server v10.5 through v10.5.5
Impact: Multiple vulnerabilities in Adobe Flash Player plug-in
Kernel
CVE-ID: CVE-2008-4218
Available for: Mac OS X v10.5 through v10.5.5, Mac OS X Server v10.5 through v10.5.5
Impact: A local user may obtain system privileges
Kernel
CVE-ID: CVE-2008-4219
Available for: Mac OS X v10.5 through v10.5.5, Mac OS X Server v10.5 through v10.5.5
Impact: Running an executable that links dynamic libraries on an NFS share may lead to an unexpected system shutdown
Libsystem
CVE-ID: CVE-2008-4220
Available for: Mac OS X v10.4.11, Mac OS X Server v10.4.11, Mac OS X v10.5 through v10.5.5, Mac OS X Server v10.5 through v10.5.5
Impact: Applications that use the inet_net_pton API may be vulnerable to arbitrary code execution or an unexpected application termination
Libsystem
CVE-ID: CVE-2008-4221
Available for: Mac OS X v10.4.11, Mac OS X Server v10.4.11, Mac OS X v10.5 through v10.5.5, Mac OS X Server v10.5 through v10.5.5
Impact: Applications that use the strptime API may be vulnerable to arbitrary code execution or unexpected application termination
Libsystem
CVE-ID: CVE-2008-1391
Available for: Mac OS X v10.4.11, Mac OS X Server v10.4.11, Mac OS X v10.5 through v10.5.5, Mac OS X Server v10.5 through v10.5.5
Impact: Applications that use the strfmon API may be exposed to an unexpected application termination or arbitrary code execution
Managed Client
CVE-ID: CVE-2008-4237
Available for: Mac OS X v10.5 through v10.5.5, Mac OS X Server v10.5 through v10.5.5
Impact: The managed screen saver settings are not applied
network_cmds
CVE-ID: CVE-2008-4222
Available for: Mac OS X v10.4.11, Mac OS X Server v10.4.11, Mac OS X v10.5 through v10.5.5, Mac OS X Server v10.5 through v10.5.5
Impact: A remote attacker may be able to cause a denial of service if Internet Sharing is enabled
Podcast Producer
CVE-ID: CVE-2008-4223
Available for: Mac OS X Server v10.5 through v10.5.5
Impact: A remote attacker may be able to access the administrative functions of Podcast Producer
UDF
CVE-ID: CVE-2008-4224
Available for: Mac OS X v10.4.11, Mac OS X Server v10.4.11, Mac OS X v10.5 through v10.5.5, Mac OS X Server v10.5 through v10.5.5
Impact: Opening an ISO file may lead to an unexpected system shutdown
