CVE-2023-6246: Heap overflow in glibc syslog due to incorrect buffer allocation size

A heap overflow vulnerability exists in glibc's syslog implementation in the __vsyslog_internal function. The vulnerability occurs when formatting log messages with a crafted LogTag (set via openlog()) combined with a large format message. The vulnerable code allocates a heap buffer based only on the header size (l) without accounting for the message size (vl), leading to a heap buffer overflow when the formatted message is written.