CVE-2026-63632 ONNX: Heap-Buffer-Overflow READ in Gemm Version Converter Adapter via Undersized Input Shape
An attacker can cause a denial of service via heap buffer overflow in ONNX version converter when processing malformed Gemm nodes with undersized input shapes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-63632?
CVE-2026-63632 is a low-severity memory corruption vulnerability in onnx, published on 18 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
Open Neural Network Exchange (ONNX) is an open standard for machine learning interoperability. From 1.3.0 until 1.22.0, onnx.version_converter.convert_version() can perform an out-of-bounds read in Gemm_7_6::adapt_gemm_7_6() in onnx/version_converter/adapters/gemm_7_6.h when a Gemm node has input tensors with fewer than two dimensions because B_shape[1], A_shape[0], or A_shape[1] is accessed without a rank check, potentially causing a process crash during an opset 7 to 6 downgrade. This issue is fixed in version 1.22.0.
Weakness: CWE-125
Which versions are affected by CVE-2026-63632?
3 open source packages ship an affected version, including onnx.
| Package | Affected | Fixed in |
|---|---|---|
onnx PyPI | From 1.3.0 | 1.22.0 |
onnx PyPI | From 1.3.0 | 1.22.0 |
onnx PyPI | From 1.3.0 | 1.22.0 |
How do I fix CVE-2026-63632?
Upgrade onnx to 1.22.0 or later.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-63632 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-63632 exists.
Sources
Also known as AZL-96728, DEBIAN-CVE-2026-63632, ECHO-2342-84be-f23c, GHSA-p893-rvq9-2xf9, PYSEC-2026-3587, UBUNTU-CVE-2026-63632.