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Vulnerability record · CVE-2026-21869 · published 8 January 2026

CVE-2026-21869: Ggml llama.cpp out-of-bounds write vulnerability

Ggml · Llama.Cpp

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.

9.8 CVSS 3.1 Critical EPSS 0.52% · top 58.4% CWE-787 · Out-of-bounds write
9.8CVSS 3.1 base score
0.52%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/ggml-org/llama.cpp/security/advisories/GHSA-8947-pfff-2f3c ExploitVendor Advisory
https://github.com/ggml-org/llama.cpp/security/advisories/GHSA-8947-pfff-2f3c ExploitVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2026-34159Ggml llama.cpp memory buffer overflow vulnerabilityllama.cpp is an inference of several LLM models in C/C++. Prior to version b8492, the RPC backend's deserialize_tensor() skips all bounds validation …EPSS 1.2%9.8CVE-2024-42478Ggml llama.cpp out-of-bounds read vulnerabilityllama.cpp provides LLM inference in C/C++. The unsafe `data` pointer member in the `rpc_tensor` structure can cause arbitrary address reading. This v…EPSS 0.60%9.8CVE-2024-42479Ggml llama.cpp out-of-bounds write vulnerabilityllama.cpp provides LLM inference in C/C++. The unsafe `data` pointer member in the `rpc_tensor` structure can cause arbitrary address writing. This v…EPSS 2.6%9.8CVE-2024-23605Ggml llama.cpp integer overflow vulnerabilityA heap-based buffer overflow vulnerability exists in the GGUF library header.n_kv functionality of llama.cpp Commit 18c2e17. A specially crafted .ggu…EPSS 1.3%9.8CVE-2024-23496Ggml llama.cpp integer overflow vulnerabilityA heap-based buffer overflow vulnerability exists in the GGUF library gguf_fread_str functionality of llama.cpp Commit 18c2e17. A specially crafted .…EPSS 1.3%9.8CVE-2024-21802Ggml llama.cpp heap-based buffer overflow vulnerabilityA heap-based buffer overflow vulnerability exists in the GGUF library info->ne functionality of llama.cpp Commit 18c2e17. A specially crafted .ggu…EPSS 1.4%9.8CVE-2024-21825Ggml llama.cpp integer overflow vulnerabilityA heap-based buffer overflow vulnerability exists in the GGUF library GGUF_TYPE_ARRAY/GGUF_TYPE_STRING parsing functionality of llama.cpp Commit 18c2…EPSS 1.3%9.8CVE-2024-21836Ggml llama.cpp integer overflow vulnerabilityA heap-based buffer overflow vulnerability exists in the GGUF library header.n_tensors functionality of llama.cpp Commit 18c2e17. A specially crafted…EPSS 1.3%

Source: NIST National Vulnerability Database (record CVE-2026-21869), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.