🛡️ CVE-2026-21869 — llama.cpp

🟠 CVSS 8.8 — High ⚠️ Exploit Public CWE-787 NVD
8.8
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. A user must be tricked into taking some action. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

Weakness class

CVE-2026-21869 is classified as CWE-787: Out-of-bounds Write. Data is written past the end or before the start of a buffer, corrupting whatever is stored there.

Affected software

CVE-2026-21869 is recorded against 1 package.

  • llama.cpp

Timeline and source

Published on 8 January 2026 and last revised on 17 June 2026. A public exploit is known to exist, which raises the urgency of patching considerably. Record sourced from NVD.

References

github.com
github.com

CVE-2026-21869 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity HIGH
CVSS Score 8.8
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CWE CWE-787
Public Exploit ⚠️ Yes
Source NVD
Published 2026-01-08
Updated 2026-08-11
Modified 2026-06-17
Fix URL N/A

Affected Packages

Software From version Fixed in
llama.cpp — —

Similar Threats

Exploit Protection

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