https://www.openwall.com/lists/oss-security/2023/10/03/2 is probably a better link (without ads and unnecessary images), which is essentially what the article is citing 1:1.
for each GLIBC_TUNABLES that it finds, it makes a copy of this variable (at line 284), calls parse_tunables() to process and sanitize this copy (at line 286), and finally replaces the original GLIBC_TUNABLES with this sanitized copy (at line 288)
To sanitize the copy of GLIBC_TUNABLES (which should be of the form "tunable1=aaa:tunable2=bbb"), parse_tunables() removes all dangerous tunables (the SXID_ERASE tunables) from tunestr, but keeps SXID_IGNORE and NONE tunables
...already made me expect what I'd see, and indeed the code there is quite unnecessarily complex. The first simplification I'd do is not make a copy of the variable's value, and the second one is to use the standard C string functions extensively; it's notable that there's no occurrence of strchr() anywhere in that function, despite it being a very useful function for parsing key-value pairs.
https://news.ycombinator.com/item?id=37754973
I guess this isn't entirely a duplicate thread though.
That one is fixed in Debian stable (and probably others):