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We've found another reason not to use Microsoft's Paint 3D – researchers

Scream if you wanna go raster: Vulnerability uncovered in unloved software

As Microsoft preps the next version of Windows, a hole has been spotted in an earlier Great Hope for the company: MS Paint 3D.

The raster graphics and 3D modelling app was part of Microsoft's Creators Update back in 2016 and was released in 2017. The idea was that users would embrace its support for 3D objects and ditch the ancient Microsoft Paint (first introduced with Windows 1.0) for the new shiny.

Things did not turn out quite that way, and Microsoft Paint continues to endure while Paint 3D looks set to follow many of the company's ambitions, ultimately shuffling quietly off into the graveyard where Zune, Band and Media Center are buried.

A vulnerability disclosed by the Zero Day Initiative (ZDI) team will not have helped matters.

The vulnerability, designated CVE-2021-31946, could let miscreants execute arbitrary code on affected versions of Paint 3D when visiting a malicious page or opening a malicious file.

The problem comes when opening STL files (a format native to the stereolithography CAD software created by 3D Systems, according to Mat Powell, senior staff vulnerability researcher at Trend Micro’s ZDI.) The issue is a good old fashioned parsing cockup where an out-of-bounds read occurs that could result in code execution in the context of the current process.

The challenge for hackers would be to persuade a user to open the file, and the attack would need to be paired with a privilege escalation to actually take over a victim's system.

The vulnerability was reported to Microsoft in February and ZDI told The Register: "We are not aware of exploits in the wild or publicly available proof-of-concept code."

The bug itself was found through fuzzing, a technique where large amounts of random data is squirted at a subject in the hope of uncovering a whoopsie.

Microsoft has now fixed the bug. The patch should slither its way onto customer's computers via the Microsoft Store.

How much longer Paint 3D itself will endure is an open question. Recent Windows Insider builds have quietly removed some 3D bits and pieces from the installation and The Register understands that while Paint endures, Paint 3D is not present in the leaked Windows 11 build.

We're pretty sure the unloved app won't be featuring on one of Microsoft's hilarious festive knitwear any time soon either. ®


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