On Tuesday morning, the Redmond technology giant issued a news bulletin announcing the release of 14 security patches, including four rated ‘critical' and eight as ‘important', as part of its Patch Tuesday programme.
Arguably the most important of all of these was a patch for a flaw in the Microsoft secure channel (Schannel) security component, which implements the Secure Sockets Layer (SSL) and transport layer security (TLS) protocols that are used to handle encryption and authentication in Windows – including on HTTP applications.
According to the Microsoft advisory, the flaw comes down to the “improper processing of specially crafted packets”, which could be exploited by attackers remotely executing attacks on targets by sending malicious traffic to a Windows-based server.
The advisory notes that the flaw (MS14-066) – which has no workaround - is ‘critical' for servers (Windows Server 2003, 2008 and 2012) and desktop devices, with the latter potentially threatening users running Vista, windows 7, 8 , 8.1 and Windows RT.
Amol Sarwate, director of engineering at Qualys, told newswire Ars Technica that these would be particularly vulnerable if the user had installed software on their client devices to monitor internet ports.
Fortunately, Microsoft says that there is no evidence pointing to in-the-wild exploits being used against Windows users at this point, although observers will note that the flaw itself comes in a year where the TLS stack (including Apple's Secure Transport, Open SSL, NSS, GNU TLS and now SChannel) have been found with varying vulnerabilities.
The update was one of 16 (two have been postponed) scheduled for the Patch Tuesday batch, which also discloses and issues fixes for two OLE bugs.
The latter affects all supported versions of Windows and is given an 'exploitability' rating of “0” as the zero-day (CVE-201406352) is being used in “limited, targeted attacks in the wild.” Specifically, the most severe of the vulnerabilities could allow for remote code execution if a user was directed to a spoofed webpage on Internet Explorer.
“An attacker who successfully exploited the vulnerabilities could run arbitrary code in the context of the current user,” reads the advisory. “If the current user is logged on with administrative user rights, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.”
Elsewhere, there are also fixes for bugs in XML Core Services (rated as critical for Vista, Windows 7, 8 and 8.1 devices), Office, Exchange and SharePoint. The full list can be seen here.
In an email to journalists, Ross Barrett, senior manager of security engineering at Rapid7, said that MS14-064 is the most critical flaw, as it relates to OLE which was exploited in the Sandworm exploit – which has been used to target Windows devices within critical infrastructure.
“The top patching priority is definitely going to be MS14-064, which is under active exploitation in the wild and may be related, at least superficially, to last month's Sandworm attack, which also worked through a vulnerability in OLE,” he said.
“After MS14-064, attention goes to MS14-065 and MS14-066, Internet Explorer and SChannel respectively. The SChannel issue is risky, since there is a very good chance that this service could be exposed or accessed via the perimeter. The IE patches are cumulative, as usual, and address 17 CVEs.
He added: “Perimeter systems are often mission critical and need the fastest attention. Administrators will have to balance the risk of exploit with their perceived exposure and their tolerance for downtime.”