Microsoft rated each of the four Security Bulletins "important," which the company defines thus: "A vulnerability whose exploitation could result in compromise of the confidentiality, integrity, or availability of users' data, or of the integrity or availability of processing resources."
The bulletins include "Vulnerabilities in Microsoft SQL Server Could Allow Elevation of Privilege" (MS08-040), "Vulnerability in Windows Explorer Could Allow Remote Code Execution" (MS08-038), "Vulnerabilities in DNS Could Allow Spoofing" (MS08-037), and "Vulnerabilities in Outlook Web Access for Exchange Server Could Allow Elevation of Privilege" (MS08-039).
While the absence of any vulnerabilities with a "critical" rating and the relatively low number of bulletins might suggest there's not much to worry about this month, Eric Schultze, CTO of Shavlik Technologies, believes Microsoft is downplaying the potential risks.
"If you consider this a light month, then Microsoft has done its job," Schultze said. "By [rating the vulnerabilities 'important,'] they hoped to lessen their visibility. It's an interesting month because there's nothing very earth-shattering but there still are important things to pay attention to."
Chief among them are the BIND DNS vulnerabilities, which affect not only Windows but Linux and Unix systems too, including Apple's Unix-based Mac OS X.
Debian, a Linux vendor, has already posted security advisories about the issue.
On Tuesday, US CERT issued a Vulnerability Note indicating that the DNS flaws affect more than 80 vendors. The Internet Systems Consortium (ISC) released several fixes for BIND9 to address the issue.
Wolfgang Kandek, CTO of Qualys, warned that the DNS vulnerabilities could be used to send an Internet user to the wrong site and that there might be no way to recognize the deception without checking the site's certificate, which few bother doing. The technique is known as DNS Poisoning.
In an e-mailed statement, Tyler Reguly, a security engineer from nCircle, elaborated on the risks of DNS poisoning. "The two DNS vulnerabilities are very serious because there is potential to poison both the DNS Server and Client," he said. "If an attacker poisons the cache of a client by spoofing a response, it only affects a single computer, but if they poison the DNS Server, they could potentially provide spoofed responses to all clients utilizing that nameserver. By using this approach an attacker could potentially compromise a corporation's entire DNS infrastructure under the right circumstances."
Schultze said that while the "important" rating may be fair for the DNS flaws themselves, a DNS poisoning attack is usually the prelude to exposure to more serious malware, which might merit a "critical" rating. He added that both the Windows Explorer and SQL server vulnerabilities mention "remote code execution," which usually is considered "critical." He said Microsoft probably softened the severity rating because exploiting the vulnerabilities is difficult.
Amol Sarwate, manager of vulnerability labs at Qualys, said he knew of two vulnerabilities that Microsoft left unpatched: CVE-2008-1436 (Windows privilege elevation vulnerability), CVE-2008-2463 (Microsoft Office Access Snapshot Viewer ActiveX control vulnerability).
Microsoft on Monday released a Security Advisory about the Snapshot Viewer flaw. It published an advisory on the Windows privilege elevation issue in April.