The vulnerability, which was not one of eight patched by Microsoft on Tuesday in the US, is in the Jet database engine component, according to an advisory posted the same day by security company Secunia. It could enable an intruder to remotely execute malicious code on a vulnerable PC, Secunia said.
Microsoft has not confirmed the existence of the security hole, which potentially affects software including Microsoft Office and the Microsoft Access database program.
Secunia rated the problem "highly critical," noting that exploit code for the flaw had been shared on a public mailing list.
"The vulnerability is caused due to a memory handling error when...parsing database files," Secunia said in its advisory. "This can be exploited to execute arbitrary code by tricking a user into opening a specially crafted '.mdb' file in Microsoft Access."
A Microsoft representative said on Tuesday in the US that the company has not heard of any attacks on customers' systems using the unpatched security hole.
"We are aware of the exploit code that has been released," the Microsoft representative said, adding that the software maker would take appropriate action once it has completed its investigation of the problem.
The original alert regarding the flaw came from a security research firm called HexView, Secunia said.
Continuing an ongoing debate about when and how flaw finders should disclose vulnerabilities, Microsoft criticised the researchers for going public with the vulnerability, rather than privately contacting the software maker so a patch could be released when the flaw was disclosed.
"It is unfortunate that this researcher decided to post publicly," the Microsoft representative said.
HexView said in its own advisory that it notified Microsoft of the flaw on 30 March, but had received no response.
A Microsoft representative said the company had no record of any contact from HexView before the flaw was publicised.
Word of the problem comes on the same day Microsoft released fixes for eight other flaws, several of them critical, and some of them revealed publicly for the first time in the company's monthly security bulletin.
CNET News.com's David Becker contributed to this report.
Now, if this product were open source, like OpenOffice.org, whoever found the problem could have identified, by line of code, where the problem actually is and fix it.
Whaddya know, that's exactly what happened in OOo case... :-)