{"id":"CVE-2026-44512","aliases":["GHSA-hwpq-hmq9-wj77","PYSEC-2026-2689"],"url":"https://o3.security/vulnerability/CVE-2026-44512","summary":"ONNX: Null Pointer Dereference in Upsample Version Converter Adapter (Zero Inputs)","details":"### Summary\n\nNull pointer dereference (SIGSEGV) in `Upsample_6_7::adapt_upsample_6_7()` (`onnx/version_converter/adapters/upsample_6_7.h:31`) when `convert_version()` processes a model with an Upsample node that has zero inputs. The adapter accesses `node->inputs()[0]->sizes()` without checking input count. 107-byte PoC crashes on Release build.\n\nThis is the same class of bug as the Cast adapter advisory (separate report) but in a different adapter, different file, and different operator.\n\n### Details\n\nThe Upsample 6→7 adapter validates attributes but not inputs:\n```cpp\n// upsample_6_7.h:20-33\nvoid adapt_upsample_6_7(..., Node* node) const {\n    ONNX_ASSERTM(\n        node->hasAttribute(width_scale_symbol) && node->hasAttribute(height_scale_symbol),\n        \"...\")  // Attribute check PASSES\n\n    auto width_scale = node->f(width_scale_symbol);\n    auto height_scale = node->f(height_scale_symbol);\n\n    auto input_shape = node->inputs()[0]->sizes();\n    //                 ^^^^^^^^^^^^^^^^^^^^\n    //                 OOB when inputs().size() == 0 → SIGSEGV\n}\n```\n\nThe PoC has an Upsample node at opset 6 with the required `width_scale` and `height_scale` attributes but zero inputs. The attribute assertions pass, then `node->inputs()[0]` on an empty `ArrayRef`:\n- Release builds (`NDEBUG`): bounds-check assertion compiled out → reads garbage pointer → SIGSEGV\n- Debug builds: `assert(Index < Length)` at `array_ref.h:159` → SIGABRT\n\nAn Upsample node with zero inputs passes `graphProtoToGraph()` because the import code only resolves input names present in the protobuf.\n\n### PoC\n```python\nimport base64\nimport onnx\nfrom onnx import version_converter\n\npoc_b64 = \"CAI6YQo8EgFZIghVcHNhbXBsZSoVCgt3aWR0aF9zY2FsZRUAAABAoAEBKhYKDGhlaWdodF9zY2FsZRUAAABAoAEBEgR0ZXN0YhsKAVkSFgoUCAESEAoCCAEKAggBCgIIBAoCCARCBAoAEAY=\"\n\nmodel = onnx.load_from_string(base64.b64decode(poc_b64))\n\n# CRASHES — Upsample_6_7 adapter dereferences empty inputs array\nversion_converter.convert_version(model, 7)  # SIGSEGV\n```\n\n107-byte PoC. Confirmed SIGSEGV on both onnx 1.21.0 (pip) and 1.22.0 (source build).\n\n### Impact\n\nAny application that uses `onnx.version_converter.convert_version()` on untrusted models is vulnerable. This includes model conversion pipelines and tools that auto-upgrade opset versions for compatibility. The crash is unrecoverable (SIGSEGV). \n\nThis vulnerability is part of a systemic pattern across multiple version converter adapters. A full audit of all ~45 adapters was performed as part of the fix; eight adapters were found with the same class of unguarded indexed access (cast_9_8, softmax_12_13, softmax_13_12, upsample_6_7, upsample_9_10, group_normalization_20_21, broadcast_forward_compatibility, upsample_9_8) and all have been fixed in PR #7813.","published":"2026-07-08T19:32:04.886Z","modified":"2026-10-21T10:02:42.784974027Z","cvss":{"score":5.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H"},"epss":{"score":0.00193,"percentile":0.09152,"asOf":"2026-09-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"onnx","fixedVersion":"1.22.0"}],"fix":{"url":"https://github.com/onnx/onnx/commit/cd310408165ad47c3cd7eb2b86cb5b80aa2e4fdf","label":"onnx/onnx@cd31040"},"references":[{"type":"WEB","url":"https://github.com/onnx/onnx/releases/tag/v1.22.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44512.json"},{"type":"ADVISORY","url":"https://github.com/onnx/onnx/security/advisories/GHSA-hwpq-hmq9-wj77"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44512"},{"type":"FIX","url":"https://github.com/onnx/onnx/commit/cd310408165ad47c3cd7eb2b86cb5b80aa2e4fdf"},{"type":"FIX","url":"https://github.com/onnx/onnx/pull/7813"},{"type":"WEB","url":"https://github.com/onnx/onnx/pull/7916"},{"type":"PACKAGE","url":"https://github.com/onnx/onnx"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T10:02:42.784974027Z"}}