With the latest Patch Tuesday release, Microsoft is fixing the FREAK vulnerability that could help attackers intercept secured network communications.
The security bulletin is one of 14 Microsoft issued Tuesday, five of which are marked critical, meaning administrators should apply them as quickly as possible.
The bulletins address vulnerabilities residing in both the consumer and server editions of Windows, Internet Explorer, Office, SharePoint Server and Exchange Server.
Discovered earlier this month, FREAK (Factoring attack on RSA-EXPORT Keys) provides a way for an attacker to intercept SSL-encrypted traffic encrypted by SSL (Secure Sockets Layer) as it moves between clients and servers.
An attacker could use the flaw to secretly access and even alter communications between two parties, said Amol Sarwate, director of engineering at security firm Qualys.
While the FREAK flaw itself resides in SSL, Microsoft has fixed the SSL implementations in its own software through MS15-031.
The critical bulletins for both Explorer (MS15-018) and Office (MS15-022) address flaws that would let an attacker take remote control of a machine, Sarwate said.
An attacker could use the vulnerabilities, for instance, to plant a malicious program onto a machine, by tricking a user into opening either an infected Web page in the case of Explorer, or an infected document in Office. “It basically turns the user’s machine into the attacker’s machine,” Sarwate said.
Although not ranked as critical, MS15-026 should be examined by administrators who oversee Exchange servers, Sarwate said. The vulnerabilities affect Exchange’s Outlook Web Access (OWA), which provides a way for users to check email with a browser. A user could be fooled into clicking on a maliciously crafted email link that directs them to the OWA site, and then extends the user’s access privileges on that machine to the attacker.
Another bulletin, MS15-030, highlights the importance of properly securing remote access connections to a server. The vulnerability resides in Microsoft Remote Desktop Protocol (RDP), which could be used to cripple a server with a denial of service (DoS) attack.
Administrators like using RDP because it provides an easy way to log into a remote machine, but if they are doing this they should employ additional security measures, such as using a virtual private network connection, said Wolfgang Kandek, Qualys chief technology officer. Keeping a port open for RDP traffic coming directly in from the Internet provides another attack surface. At the minimum, RDP users should apply this patch.