UBUNTU-CVE-2026-116816: High severity ubuntu/llama.cpp vulnerability

llama.cpp b5899 before b10261 contains a heap out-of-bounds write vulnerability in llmtokenizerplamo2::build that allows attackers to corrupt heap memory via crafted GGUF models. Attackers can supply BYTE-typed token text like <0x-1> whose negative parsed value writes token ids before the bytes buffer during model loading, causing crashes or potential code execution.