CVE-2026-63632Public exploit

Process crash via unchecked Gemm shape indexing

Published Aug 18, 2026 · Updated Aug 18, 2026

Out-of-bounds read in ONNX 1.3.0 through 1.21.0 allows attackers to crash a process via a malformed Gemm node during opset downgrade. In Gemm_7_6::adapt_gemm_7_6() in onnx/version_converter/adapters/gemm_7_6.h, the Gemm 7 to 6 adapter indexes B_shape[1], A_shape[0], and A_shape[1] without verifying that the input tensors have at least two dimensions. Exposure is limited to applications that call onnx.version_converter.convert_version() on untrusted models for a 7 to 6 conversion, where the documented outcome is a crash or runtime abort rather than code execution.

CVSS severity3.3
Low
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in ONNX 1.3.0 through 1.21.0 allows attackers to crash a process via a malformed Gemm node during opset downgrade. In Gemm_7_6::adapt_gemm_7_6() in onnx/version_converter/adapters/gemm_7_6.h, the Gemm 7 to 6 adapter indexes B_shape[1], A_shape[0], and A_shape[1] without verifying that the input tensors have at least two dimensions. Exposure is limited to applications that call onnx.version_converter.convert_version() on untrusted models for a 7 to 6 conversion, where the documented outcome is a crash or runtime abort rather than code execution.

The record

CVE
CVE-2026-63632
Published
Aug 18, 2026
Updated
Aug 18, 2026
Vendor
ONNX
Product
ONNX
Classifications
CWE-125, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 1.3.0, < 1.22.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

ONNX · ONNXversion=>= 1.3.0, < 1.22.0

Published CVSS scores

3.3GitHub Advisory DatabaseCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1204.002User Execution: Malicious File

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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