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October 5, 2009

Users of Internet Explorer and other Web browsers' computers still remain vulnerable because Microsoft hasn't patched an underlying security hole, even after more than two months that a hacker easily demonstrated how to spoof SSL authentication certificates for almost any eCommerce website on the Internet.

The security hole that is causing all the problems resides in an application programming interface (API) known as CryptoAPI, and it causes Microsoft's Internet Explorer and other browsers that rely on the SSL code to be tricked by fraudulent secure sockets layer certificates.

It can be exploited in a number of various ways to impersonate websites, virtual private networks and even email servers by adding a null character to the prefix of an address in a legitimate SSL credential.

Why or how the bug still hasn't been fixed as of today still remains unknown at this time and it now has the security community up in arms.

"There are literally thousands of products on Windows right now that are still vulnerable to this SSL certificate vulnarability, and if someone were to publicly publish a targeted null prefix certificate, they'd be in trouble," said the white-hat hacker, who goes by the moniker Moxie Marlinspike.

"Basically, everything that runs on Windows would be vulnerable with that one certificate, he added."

Among the Web browsers that still rely on the Microsoft library to parse SSL certificates are Google Chrome and Apple Safari for Windows. Mozilla's Firefox browser dosen't appear that have that vulnarability for now.

The security hole stems from code that causes browsers, email clients and other SSL-enabled applications to simply ignore all characters following the \ and 0 characters, which are used to denote the end of a sequence of characters in C-based languages.

In contrast, some issuers of SSL certificates look at the entire domain name whether or not it contains the null character and then makes its decision based on the underlying facts.

The security hole would cause both browsers to display a fraudulently authenticated website with no warning that anything was wrong. The Firefox browser, by contrast, fixed vulnerabilities related to the null character bug a few days after Marlinspike presented his demo at the Black Hat security conference in late July.

The code discrepancy allows any potential attacker to obtain a SSL certificate for a website under his control and then append the target site and a "\0" to the the address.

Marlinspike, who holds legitimate claim to the domain thoughtcrime.org, said the common name field for a certificate targeting Bank of America's site would read:

www.bankofamerica.com\*thoughtcrime.org.

"The fact that would be truly damaging for them would be if somebody would soon release a targeted null prefix certificate for Bank of America," he said.

"That would affect all Microsoft products that are still unpatched," added Marlinspike.

It still remains unclear for now when this security vulnarability will be repaired for good.

There are some Internet security observers that now think it could take Microsoft another month or two to fix this hole.

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Source: ISNG.

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