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High · 8.8 CVE-2026-21869 EUVD-2026-1661

llama.cpp has Out-of-bounds Write in llama-server

Published Jan 7, 2026 · Updated Jan 8, 2026 · Assigned by GitHub_M

Description

llama.cpp is an inference of several LLM models in C/C++. In commits 55d4206c8 and prior, the n_discard parameter is parsed directly from JSON input in the llama.cpp server's completion endpoints without validation to ensure it's non-negative. When a negative value is supplied and the context fills up, llama_memory_seq_rm/add receives a reversed range and negative offset, causing out-of-bounds memory writes in the token evaluation loop. This deterministic memory corruption can crash the process or enable remote code execution (RCE). There is no fix at the time of publication.

Affected products

VendorProductAffectedFixed
ggml-org llama.cpp <= 55d4206c8 —

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Debian 14 llama.cpp 7593+dfsg-1 —
ReleasePackageFixed inAdvisory
Ubuntu 26.10 llama.cpp No fix yet —
Ubuntu 26.04 LTS llama.cpp No fix yet —
Ubuntu 25.10 llama.cpp No fix yet —
ReleasePackageFixed inAdvisory
openSUSE Tumbleweed llamacpp 9500-1.1 openSUSE-SU-2026:10961-1

Advisories 1

References