Hackerone: CVE-2024-6197 Freeing stack buffer in utf8asn1str

libcurl's ASN1 parser has this utf8asn1str() function used for parsing anASN.1 UTF-8 string. Itcan detect an invalid field and return error.Unfortunately, when doing so it also invokes `free()` on a 4 bytelocalstack buffer. Most modern malloc implementations detect this errorand immediately abort. Some however accept the input pointer and add thatmemory to its list of available chunks. This leads to the overwriting ofnearby stack memory. The content of the overwrite is decided by the`free()` implementation; likely to be memory pointers and a set of flags.The most likely outcome of exploting this flaw is a crash, although itcannot be ruled out that more serious results can be had in specialcircumstances.

Where it's fixed