In PHP versions 8.2.* before 8.2.31, 8.3.* before 8.3.31, 8.4.* before 8.4.21, and 8.5.* before 8.5.6, some functions, including urldecode(), pass signed char to ctype functions (like isxdigit()). On the systems with default signed char and optimized table-lookup ctype functions - such as NetBSD - this can lead to accessing array with negative offset, which can trigger a denial of service.