Project Zero just unrestricted the details on CVE-2021-24093, a potentially nasty vulnerability in Windows 10’s DirectWrite, a text rendering library. The flaw got fixed in this month’s patch Tuesday roundup. The flaw is accessible in all the major browsers on Windows 10, as they use DirectWrite for font rendering. The trick here is to use a malicious font that uses some nonsense values. Those values result in a buffer allocation that is too small for complex characters such as Æ.
Because the vulnerability is a Windows library, it’s possible that an exploit would automatically work as a sandbox escape, but I haven’t seen confirmation either way. Let us know if you have some insight there.
GNU Poke
The good folks at GNU have minted the 1.0 release of poke, a new binary editing tool. The real killer feature of poke is that it can interpret binary data, decoding it back into readable data structures. If you’re familiar with the way Wireshark can decode packets and give useful, organized output, it seems that poke will provide a similar function, but not limited to network traffic.
It looks like it could become a useful tool for getting a look inside otherwise opaque binaries. What poke brings is a system where you can write pretty-printing templates on the fly, which should be very useful when mapping out an unfamiliar binary. Distros will likely pick up and start packaging poke in the coming weeks, making it even easier to get and play with. Continue reading “This Week In Security: Text Rendering On Windows, GNU Poke, And Bitsquatting”
