Noob question: that's a really old library, right? Has this issue been there for decades before someone found it, or is this vulnerability part of some newer addition to it?
Edit: I didn't understand the first sentence of the article so I figured I wouldn't understand any of it -- but my question is answered pretty early on:
It's said to have been accidentally introduced in August 2022 with the release of glibc 2.37.
glibc is the library that provides basic functionality for C programs. It provides the bottom level implementation for things like opening files, requesting memory, and other OS-level stuff.
glibc isn't the only implementation out there. Even on Linux, there are other options, such as muslc.
It gets updated regularly, as the C standard or operating system needs. So while it has been around for a very long time (by software standards anyway) it's still an active and evolving piece of software. --and one that underpins many critical functions of our systems.