CVE-2026-2069 | ggml-org llama.cpp up to 55abc39 GBNF Grammar llama-grammar.cpp llama_grammar_advance_stack stack-based overflow (Issue 18988 / ID 18993)

A vulnerability marked as critical has been reported in ggml-org llama.cpp up to 55abc39. Impacted is the function llama_grammar_advance_stack of the file llama.cpp/src/llama-grammar.cpp of the component GBNF Grammar Handler. This manipulation causes stack-based buffer overflow.

This vulnerability is registered as CVE-2026-2069. The attack needs to be launched locally. Furthermore, an exploit is available.

To fix this issue, it is recommended to deploy a patch.