Race Condition Use-After-Free in llama.cpp LLaMA-Android JNI

Publication date: 2026-08-06

Last updated on: 2026-08-06

Assigner: VulnCheck

Description

llama.cpp builds b1886 through b7445 contain a race condition use-after-free vulnerability in the LLaMA-Android JNI wrapper where bench_1model() and free_1context() lack synchronization, allowing Thread A to operate on freed memory while Thread B concurrently frees the llama_context. Attackers can exploit this by performing heap spray with attacker-controlled data containing a fake vtable to hijack the vtable pointer at offset +0x30, causing llama_batch_allocr::clear() to dereference arbitrary memory and achieve remote code execution.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-08-06

Last Modified

2026-08-06

Generated

2026-08-07

AI Q&A

2026-08-07

EPSS Evaluated

N/A

NVD

CVE-2026-70640

Affected Vendors & Products

Vendor	Product	Version / Range
llama	llama_cpp	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-362	The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
CWE-476	The product dereferences a pointer that it expects to be valid but is NULL.

Attack-Flow Graph

Executive Summary

This is a race condition use-after-free vulnerability in llama.cpp versions b1886 through b7445. It occurs in the LLaMA-Android JNI wrapper where two functions, bench_1model() and free_1context(), lack proper synchronization. This allows one thread to access freed memory while another thread frees the llama_context, potentially enabling attackers to execute arbitrary code by manipulating memory.

Impact Analysis

If exploited, this vulnerability could allow attackers to execute remote code on your system. This might lead to unauthorized access, data theft, or system compromise. Users of vulnerable versions of llama.cpp, especially those using the LLaMA-Android JNI wrapper, are at risk.

Mitigation Strategies

Update llama.cpp to a version beyond b7445 to address the race condition and use-after-free vulnerability in the LLaMA-Android JNI wrapper.

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