Microsoft issued patches April 13 to cover 25 security holes across Windows, Office and Exchange.
Five of the 11 security bulletins issued were rated critical, and Microsoft is calling administrators' attention to three in particular: MS10-026, MS10-027 and MS10-019. All three vulnerabilities can leave users open to remote code execution by attackers. They affect Microsoft MPEG Layer-3 audio codecs, Windows Media Player and Windows Authenticode Verification, respectively.
"MS10-019 is very interesting as well as disturbing," said Jason Miller, data and security team leader at Shavlik Technologies, explaining that an attacker could use the two vulnerabilities the bulletin addresses to bypass digitally signed files.
"An attacker can modify the signed file and not invalidate the digital signature," Miller said. "It is very common to rely on a digital signature to verify the integrity of the file. If the signature is valid, the file came from the original source, making this a simple and secure process. However, with this vulnerability, attackers can trick people into thinking the file is valid. With this bulletin, systems will have two patches required to fix this vulnerability, which are Authenticode Signature Verification and Cabinet File Viewer Shell Extension."
MS10-019 scored a 2 on the company's exploitability index, while MS10-026 and MS10-027 received a 1, Microsoft's highest rating. Microsoft warned that the vulnerability in the MPEG Layer-3 audio codecs (MS10-026) could be exploited via malicious AVI file with an MPEG Layer-3 audio stream. While Windows 7, Windows Server 2008 R2 and the Itanium versions of Windows Server 2003 and 2008 are not affected, the bulletin is critical for Windows 2000, Windows XP, and Server 2003 and 2008 users.
MS10-027 fixes a critical Windows Media Player vulnerability that could allow remote code execution if a user opened specially crafted media content hosted on a malicious Website. The bug only impacts Windows 2000 and XP users.
The other critical bulletins cover a vulnerability in Microsoft Windows Services running on Windows 2000 Server and a vulnerability in the SMB protocol the company warned users about in November. Also among the fixes is a bug rated important that affects VBScript and that Microsoft issued an advisory about in March.