Apple released new versions of Safari for Mac OS X to fix critical vulnerabilities that could allow Web attackers to execute malicious code on computers. Patches are not yet available for Apple’s iOS mobile OS, which is likely affected by some of the same flaws.

The Safari 6.1.4 and 7.0.4 updates that were released Wednesday for OS X Lion v10.7.5, OS X Lion Server v10.7.5, OS X Mountain Lion v10.8.5 and OS X Mavericks v10.9.3 fix a total of 22 vulnerabilities.

Twenty-one of those flaws are memory corruption issues that could be exploited to crash the browser and execute arbitrary code on the system when users visit maliciously crafted websites, according to a security advisory published by Apple.

All of the newly patched vulnerabilities are actually located in WebKit, the Web content rendering engine that powers Safari, but which is also used in iOS and some other Apple products.

WebKit was also used by Google Chrome until version 27, when it switched to a new rendering engine called Blink, which is heavily based on WebKit. This explains why the Google Chrome Security Team and other regular Chrome bug hunters are credited with finding most of the new vulnerabilities fixed in Safari.

The lack of similar security updates for iOS, which is likely also affected by at least some of the same WebKit vulnerabilities, could potentially put users of the latter platform at risk.

Former Apple security researcher Kristin Paget strongly criticized the company last month for leaving iOS users exposed for three weeks to WebKit vulnerabilities that had been patched in Safari 6.1.3 and 7.0.3.

This patching discrepancy for the same flaws across different products is a recurrent issue for Apple. There were patching delays of more than two months between Safari and iOS in the past.

Security researchers have argued for a long time that it’s relatively easy for attackers to reverse engineer patches and build exploits for the vulnerabilities they address, but when those same flaws are present in other products for which patches are not available the risks are obviously greater.