ONNX ConvTranspose shape inference has out-of-bounds read CVE-2026-115920

A CVE-2026-115920 out-of-bounds read (CVSS 6.2) affects ONNX versions 1.2.1 through 1.21.x: shape inference for ConvTranspose with a weight tensor of rank below three and no kernel_shape reads past an empty vector and crashes the process. It is fixed in ONNX 1.22.0.

• CWE-125 flaw affects ONNX 1.2.1 to 1.21.x, patched in 1.22.0
• Triggered by a ConvTranspose weight tensor of rank below three without kernel_shape
• Exploitation causes SIGSEGV denial of service; a POC exists
• CVSS 6.2, EPSS 0.18%, not listed in CISA KEV