More fixes are appearing for a pair of highly dangerous vulnerabilities exposed earlier this month in the Android mobile operating system.

Security vendor Webroot and ReKey, a collaboration between Northeastern University in Boston and vendor Duo Security, released software on Tuesday that detects if an Android device is vulnerable and applies a patch.

Google, which manages the open-source Android project, quickly issued patches for the so-called “master key” vulnerabilities, one of which was found by Bluebox Security and another one that appeared on a Chinese-language forum.

But mobile phone manufacturers and operators are often very slow in releasing patches to their users, a problem that is likely to become more critical as mobile device use rises.

The result is a large number of users running vulnerable devices. More than 156 million Android smartphones were sold in the first three months of this year worldwide, amounting to a 74 percent market share, according to analyst Gartner.

The vulnerability found by Bluebox may affect more 900 million devices made over the last four years running Android versions 1.6 and higher.

The vulnerabilities are particularly dangerous since they allow an attacker to modify an Android package file, which is used to install an application, without affecting its original cryptographic signature.

The signature is generated by the application’s author and is used to verify the program’s integrity. By using the vulnerability and maliciously modifying an application, a hacker could gain complete control over an Android device.

ReKey is an application that applies the Google patches. It also will alert users if an application tries to install itself using the vulnerabilities. ReKey needs root access to a device, which is normally not granted to most applications, in order to patch vulnerabilities.

Webroot wrote on Tuesday that it has deployed a patch within its SecureAnywhere Mobile product, which also covers Android’s Jelly Bean 4.1 and Ice Cream Sandwich releases.

Bluebox also has an application that detects if a device is vulnerable and scans for malicious applications.

In order to protect users, Google is scanning applications in its Play store to ensure those programs are legitimate. Android also has a feature, called ”Verify Apps,” which allows Google to vet applications before installation.

Application markets and websites not run by Google have posed a risk for Android users. Security researchers have found numerous examples of popular applications that have been modified to deliver secret code that can spy on users.

Send news tips and comments to jeremy_kirk@idg.com. Follow me on Twitter: @jeremy_kirk