Microsoft today issued 13 security updates that patched 22 vulnerabilities in Internet Explorer, Windows, Office and other software, including one that harked back two decades to something dubbed "Ping of Death."
Of Tuesday's 13 updates, called "bulletins" by Microsoft, two were labeled "critical" -- the most-serious rating in the company's four-step score -- nine were marked "important," the next-most-dangerous category, and two were pegged as "moderate."
Three of the 22 individual vulnerabilities patched today in the baker's dozen of bulletins were rated critical. The remainder were split -- 15 and four, respectively -- between important and moderate.
Researchers today called out MS11-057, which patches seven flaws in Internet Explorer (IE), as the most important to patch pronto.
"This is the anticipated IE update, about what we expected," said Andrew Storms, director of security operations at nCircle Security, referring to Microsoft's habit of updating its browser every two months. "The most important thing here is that it affects IE9."
Today's IE update was the second to patch critical vulnerabilities in IE9 on Vista and Windows 7. Microsoft first fixed a critical IE9 bug in June.
"MS11-057 affects all Windows versions, and all it takes is a malicious [Web] page to take control of a PC," echoed Wolfgang Kandek, chief technology officer for Qualys. "It's a no-brainer to put this at the top of the list."
Other security experts from Symantec and Kaspersky Lab also highlighted the IE update as the one users should deploy first.
"Both of [the critical vulnerabilities] can be exploited by a drive-by download," said Joshua Talbot, security intelligence manager with Symantec's security response team, in an email. "The fact that vulnerabilities such as these continue to be so common is one reason why web-based attacks are so prevalent."
Drive-by download attacks are those that can be triggered simply by steering a vulnerable browser to a malicious website. Users are typically duped into visiting such sites by search poisoning efforts or links embedded in spammed email messages.
Most experts, including those on Microsoft's payroll, called out MS11-058 as the second update to apply as soon as possible.
That update patches a pair of vulnerabilities in Microsoft's DNS (domain name system) service, which is used by many organizations to translate Internet addresses into the domains recognizable to humans.
Microsoft ranked one of the MS11-058 bugs as critical on Windows Server 2008 and Server 2008 R2 when running the DNS service, and warned that attackers could remotely exploit such servers simply by sending it a malformed query.
"[That] could potentially allow an attacker who successfully exploited the vulnerability to run arbitrary code on Windows Server 2008 and Windows Server 2008 R2 DNS servers having a particular DNS configuration," said Microsoft in a follow-up post to its Security Research & Defense blog today.
"This is significant, as the majority of organizations running Microsoft-based networks do have DNS activated on their servers," said Marcus Carey, a security researcher with Rapid7, in an email today.