glibc qsort() Out-Of-Bounds Read / Write

Qualys discovered a memory corruption in the glibc's qsort() function, due to a missing bounds check. To be vulnerable, a program must call qsort() with a nontransitive comparison function (a function cmp(int a, int b) that returns (a - b), for example) and with a large number of attacker-controlled elements (to cause a malloc() failure inside qsort()). They have not tried to find such a vulnerable program in the real world. All glibc versions from at least September 1992 (glibc 1.04) to the current release (glibc 2.38) are affected, but the glibc's developers have independently discovered and patched this memory corruption in the master branch (commit b9390ba, "stdlib: Fix array bounds protection in insertion sort phase of qsort") during a recent refactoring of qsort().