LIBPNG has use-after-free via pointer aliasing in `png_set_tRNS` and `png_set_PLTE`

{
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "cveMetadata": {
    "cveId": "CVE-2026-33416",
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "dateUpdated": "2026-03-26T19:52:10.961Z",
    "dateReserved": "2026-03-19T17:02:34.172Z",
    "datePublished": "2026-03-26T16:48:54.174Z",
    "state": "PUBLISHED"
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        "shortName": "GitHub_M",
        "dateUpdated": "2026-03-26T16:48:54.174Z"
      },
      "title": "LIBPNG has use-after-free via pointer aliasing in `png_set_tRNS` and `png_set_PLTE`",
      "descriptions": [
        {
          "lang": "en",
          "value": "LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. In versions 1.2.1 through 1.6.55, `png_set_tRNS` and `png_set_PLTE` each alias a heap-allocated buffer between `png_struct` and `png_info`, sharing a single allocation across two structs with independent lifetimes. The `trans_alpha` aliasing has been present since at least libpng 1.0, and the `palette` aliasing since at least 1.2.1. Both affect all prior release lines `png_set_tRNS` sets `png_ptr->trans_alpha = info_ptr->trans_alpha` (256-byte buffer) and `png_set_PLTE` sets `info_ptr->palette = png_ptr->palette` (768-byte buffer). In both cases, calling `png_free_data` (with `PNG_FREE_TRNS` or `PNG_FREE_PLTE`) frees the buffer through `info_ptr` while the corresponding `png_ptr` pointer remains dangling. Subsequent row-transform functions dereference and, in some code paths, write to the freed memory. A second call to `png_set_tRNS` or `png_set_PLTE` has the same effect, because both functions call `png_free_data` internally before reallocating the `info_ptr` buffer. Version 1.6.56 fixes the issue."
        }
      ],
      "affected": [
        {
          "vendor": "pnggroup",
          "product": "libpng",
          "versions": [
            {
              "version": ">= 1.2.1, < 1.6.56",
              "status": "affected"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "lang": "en",
              "description": "CWE-416: Use After Free",
              "cweId": "CWE-416",
              "type": "CWE"
            }
          ]
        }
      ],
      "references": [
        {
          "url": "https://github.com/pnggroup/libpng/security/advisories/GHSA-m4pc-p4q3-4c7j",
          "name": "https://github.com/pnggroup/libpng/security/advisories/GHSA-m4pc-p4q3-4c7j",
          "tags": [
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        {
          "url": "https://github.com/pnggroup/libpng/pull/824",
          "name": "https://github.com/pnggroup/libpng/pull/824",
          "tags": [
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          "url": "https://github.com/pnggroup/libpng/commit/23019269764e35ed8458e517f1897bd3c54820eb",
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          "url": "https://github.com/pnggroup/libpng/commit/7ea9eea884a2328cc7fdcb3c0c00246a50d90667",
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          "url": "https://github.com/pnggroup/libpng/commit/a3a21443ed12bfa1ef46fa0d4fb2b74a0fa34a25",
          "name": "https://github.com/pnggroup/libpng/commit/a3a21443ed12bfa1ef46fa0d4fb2b74a0fa34a25",
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        {
          "url": "https://github.com/pnggroup/libpng/commit/c1b0318b393c90679e6fa5bc1d329fd5d5012ec1",
          "name": "https://github.com/pnggroup/libpng/commit/c1b0318b393c90679e6fa5bc1d329fd5d5012ec1",
          "tags": [
            "x_refsource_MISC"
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            "version": "3.1",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H",
            "attackVector": "NETWORK",
            "attackComplexity": "HIGH",
            "privilegesRequired": "NONE",
            "userInteraction": "REQUIRED",
            "scope": "UNCHANGED",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH"
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    "adp": [
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          "dateUpdated": "2026-03-26T19:52:10.961Z"
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