Security consultants have independently confirmed a serious security weakness that makes it trivial for hackers with physical control of many computers sold by Dell, Acer, and at least 14 other manufacturers to quickly recover Windows account passwords.

The vulnerability is contained in multiple versions of fingerprint-reading software known as UPEK Protector Suite. In July, Apple paid $356 million to buy Authentec, the Melbourne, Florida-based company that acquired the technology from privately held UPEK in 2010. The weakness came to light no later than September, but Apple has yet to acknowledge it or warn end users how to work around it. No one has accused Apple of being responsible for the underlying design of fingerprint-reading software.

The UPEK software has long been marketed as a secure means for logging into Windows computers using an owner's unique fingerprint, instead of a user-memorized password. Last month, Elcomsoft, a Russia-based developer of password-cracking software, warned that the software makes users less secure than they otherwise would be because it stores Windows account passwords to the registry and encrypts them with a key that is easy for hackers to retrieve. It takes only seconds for people with the key to extract a password, company officials said. They withheld technical details to prevent the vulnerability from being widely exploited.

Now, a pair of security consultants say they have independently verified the vulnerability and released open-source software that makes it easy to exploit it. Easily decrypted passwords are stored in one of several registry keys located in HKEY_LOCAL_MACHINE\Software\Virtual Token\Passport\, depending on the application version. The duo said they released the software and additional information so that penetration testers, who are paid to penetrate the defenses of their customers, can exploit the weakness.

"From a penetration testing perspective, local administrator access is required to obtain the necessary registry key's value, so it only matters if you already have control of the PC," Brandon Wilson, one of the security consultants, told Ars. "But since so many of these devices are used in corporate environments, it makes it easy to obtain domain credentials, and from there, easily expand an attack to other systems."

When Protector Suite isn't activated, Windows doesn't store account passwords in the registry unless users have specifically configured an account to automatically log in. Security experts have long counseled people not to use automatic log in. Disabling Windows login functionality from within Protector Suite will not remove the password from the registry key, the penetration testers confirmed. If the "passport" for that user is deleted from within the application, the password is also deleted. When uninstalling the application, an option is presented to the user to also delete the passport data. If left, the password remains, and if removed, the password is deleted, Wilson said.

According to Wilson, every version of the software labeled "UPEK Protector Suite" that he and fellow penetration tester Adam Caudill have analyzed has tested positive for the vulnerability. In addition to Dell and Acer, other PC makers that preinstall the software include Amoi, Asus, Clevo, Compal, Dell, Gateway, IBM/Lenovo, Itronix, MPC, MSI, NEC, Sager, Samsung, Sony, and Toshiba. UPEK Protector Suite is also rebranded by Lenovo as ThinkVantage Fingerprint Software, Wilson said.

Given the claims made in the UPEK software that it's a safe alternative to account logins, it's surprising there has been no recall or an advisory warning of the vulnerability. Representatives from Apple and Authentec didn't respond to an e-mail seeking comment for this brief.

Update October 11, 2012: As reported elsewhere on Wednesday night, Authentic issued a patch for UPEK Protector Suite in mid September. Adam Caudill, one of the penetration testers who independently confirmed the vulnerability, told Ars they were unaware of that release until Wednesday night. In an e-mail, he described the patch as a "band-aid" because under the new version, passwords are protected using encryption that's trivial to brute force. More details from the Threat Post blog are here. What's more, the patch has yet to be pushed out to many users, and Ars isn't aware of any advisories warning of the vulnerability or advising users to install the newer version.

Story updated to add details in the second and last paragraphs.