A flaw has been found 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. The attack needs to be launched locally. The exploit has been published and may be used. Patch name: 18993. To fix this issue, it is recommended to deploy a patch.

References

• https://nvd.nist.gov/vuln/detail/CVE-2026-2069
• ggml-org/llama.cpp#18988
• ggml-org/llama.cpp#18988 (comment)
• ggml-org/llama.cpp#18993
• https://github.com/ggml-org/llama.cpp
• https://github.com/user-attachments/files/24761101/poc.zip
• https://vuldb.com/?ctiid.344636
• https://vuldb.com/?id.344636
• https://vuldb.com/?submit.745263