![]() “Kind of like early web browsers, when JavaScript first came out,” Munin explained to Salted Hash. The problem is the un-sandboxed feature and network awareness, which is why it can accept URLs (external or local). Regsvr32 is whitelisted, seen as an essential system function. “Please note, the exploit described does not make any changes to the registry monitoring of registry entries will not be effective,” wrote an information security consultant who is known as Munin. Salted Hash as reached out to Microsoft for comment, and we’ll update this story if they chose to respond. As Smith wrote, it doesn’t alter the registry, it doesn’t require administrative privileges, and the scripts can be called over HTTP or HTTPS. If used, this command will make Red Team engagements a bit easier, and the same can be said about criminal attacks. Smith published several proof-of-concept scripts, which other researchers confirmed work as expected. This makes for some interesting developments, because all an attacker has to do is place the code block (VP or JS) inside the registration element. ![]() Until now, few people – if any – knew that Regsvr32 could accept a URL for a script. sct file at a location you control,” Smith wrote. ![]() … And … You guessed a signed, default MS binary. “The amazing thing here is that regsvr32 is already proxy aware, uses TLS, follows redirects, etc. After some trial an error, he discovered an interesting solution: If the technique is used, there’s little evidence left behind for investigators, as the process doesn’t alter the system registry and in some cases comes across as normal Internet Explorer traffic.Ĭasey Smith needed to install a reverse shell, but the workstation in question was locked down by AppLocker and script rules. A US researcher in Colorado has discovered a feature in Regsvr32 that allows an attacker to bypass application whitelisting protections, such as those afforded by Microsoft’s AppLocker. ![]()
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