Microsoft Reassesses the Exploitability of Two Vulnerabilities

Microsoft updated the exploitability index of two vulnerabilities patched last week in light of new information and added additional information for a third.

On September 15, Microsoft released patches for twelve vulnerabilities in various Windows, IIS and Office components, which were covered in nine security bulletins.

Four of these vulnerabilities had a severity rating of critical, but the creation of reliable exploits for two them was considered unlikely.

Yesterday, Microsoft updated the exploitability index for one of these vulnerabilities (CVE-2010-2738), described in MS10-063, after receiving additional research from Secunia.

"During analysis of MS10-063 is was discovered that Microsoft had fixed two very similar array-indexing vulnerabilities in different functions.

"Upon further analysis, it was concluded that at least one of the fixed vulnerabilities could be exploited in a reliable manner and not an unreliable (inconsistent) manner as evaluated by Microsoft.

"On Friday 17th September, Secunia Research contacted Microsoft and provided full details on the performed analysis to work with the vendor on raising the exploitability index rating to 1 (consistent exploit code likely) in order to ensure that customers would properly prioritise the update," Secunia announced.

However, while this might be the most important change in terms of priority – CVE-2010-2738 (MS10-063) now being a critical vulnerability with a high exploit probability – it is not the only modification made by Microsoft to its recent security bulletins.

The vendor also lowered the exploitability index from 1 to 2 for CVE-2010-2730 (MS10-065), a buffer overflow in Internet Information Services (IIS) 7.5 with FastCGI enabled, which can lead to remote code execution.

The exploitability key note for CVE-2010-0818 (MS10-062), another critical vulnerability in the MPEG-4 Codec, was modified to specify that code execution on Vista is less likely due to additional heap mitigations.