Pillow: Heap out-of-bounds write in Pillow `ImageFilter.RankFilter` via integer overflow in `ImagingExpand`

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  "url": "https://osv.dev/vulnerability/CVE-2026-59197",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Pillow: Heap out-of-bounds write in Pillow `ImageFilter.RankFilter` via integer overflow in `ImagingExpand`",
    "summary": "Pillow is a Python imaging library. Prior to 12.3.0, Pillow's public rank-filter API can trigger a native heap out-of-bounds write when given a very large odd filter size because ImageFilter.RankFilter.filter() calls image.expand(size // 2, size // 2) before rank-filter size validation and ImagingExpand() computes output dimensions with unchecked signed int arithmetic. This issue is fixed in version 12.3.0.",
    "evidence": "osv:CVE-2026-59197",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-59197",
      "aliases": [
        "BIT-pillow-2026-59197",
        "CVE-2026-59197",
        "GHSA-xj96-63gp-2gmr",
        "PYSEC-2026-3454"
      ],
      "metrics": [
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          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H"
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-59197.json"
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      "modified": "2026-10-28T02:30:45.586822914Z",
      "provider": "osv",
      "references": [
        "https://github.com/python-pillow/Pillow/releases/tag/12.3.0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59197.json",
        "https://github.com/python-pillow/Pillow/security/advisories/GHSA-xj96-63gp-2gmr",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-59197",
        "https://github.com/python-pillow/Pillow/commit/cce3bdb867c77a3420261ed1bfdb6b0787ec8fc1",
        "https://github.com/python-pillow/Pillow/pull/9695"
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      "provider_metadata": {
        "cwe_ids": [
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  "source_id": "core-osv",
  "document_id": 513804,
  "published_at": "2026-07-14T16:25:23.52+00:00"
}