Software Engineering Institute

Overview

An out-of-bounds (OOB) memory access vulnerability involving unchecked array indexing has been identified in the exllamav3_ext compute unified device architecture (CUDA) extension. Successful exploitation can lead to an immediate denial of service or application instability. This vulnerability is tracked as CVE-2026-84286.

Description

An OOB memory access vulnerability exists in the exllamav3_ext module due to insufficient input validation.

When the kernel parameter K is set to 0 in a crafted input, the extension generates a negative array index, resulting in a CUDA illegal memory access.s. The root cause is a missing bounds check in the kernel-table dispatch process. The checkpoint-derived block index (cbi) is used to access a fixed 24-entry array without confirming that either K or cbi fall within safe limits.

Impact

Primary impacts include Denial of Service (DoS) through process crashes and potential unstable execution states within applications utilizing the library.

Solution

The vendor has addressed this vulnerability in the main repository. Users are advised to update their installations or apply the fix from the merged pull request: https://github.com/turboderp-org/exllamav3/pull/310.

Supply chain

Downstream projects utilizing this library are indirectly exposed to this vulnerability. According to the ExLlamaV3 Dependency Graph, there are 49 total dependencies currently tracking this repository. Notable downstream projects directly affected by this supply chain link include: UnstableLlama / ezexl3 and Ednaordinary / MawDiscord
Developers and maintainers of these dependent repositories are strongly encouraged to rebuild their packages against the patched version of exllamav3_ext.

Acknowledgements

The CERT Coordination Center (CERT/CC) thanks Nathan Keys (professor-moody) for discovering and responsibly reporting this vulnerability.
This AI-assisted vulnerability note was prepared by Laurie Tyzenhaus.

Vendor Information