{"id":"CVE-2026-33416","state":"PUBLISHED","title":"LIBPNG has use-after-free via pointer aliasing in `png_set_tRNS` and `png_set_PLTE`","description":"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.","publishedAt":"2026-03-26T16:48:54.174Z","updatedAt":"2026-04-01T03:55:17.603Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H","source":"GitHub_M"},"assigner":"GitHub_M","products":["pnggroup libpng"],"affected":[{"vendor":"pnggroup","product":"libpng","versions":[{"version":">= 1.2.1, < 1.6.56","status":"affected"}]}],"references":["https://github.com/pnggroup/libpng/security/advisories/GHSA-m4pc-p4q3-4c7j","https://github.com/pnggroup/libpng/pull/824","https://github.com/pnggroup/libpng/commit/23019269764e35ed8458e517f1897bd3c54820eb","https://github.com/pnggroup/libpng/commit/7ea9eea884a2328cc7fdcb3c0c00246a50d90667","https://github.com/pnggroup/libpng/commit/a3a21443ed12bfa1ef46fa0d4fb2b74a0fa34a25","https://github.com/pnggroup/libpng/commit/c1b0318b393c90679e6fa5bc1d329fd5d5012ec1"],"weaknesses":["CWE-416"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/33xxx/CVE-2026-33416.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-33416","state":"PUBLISHED","datePublished":"2026-03-26T16:48:54.174Z","dateUpdated":"2026-04-01T03:55:17.603Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-03-19T17:02:34.172Z"},"containers":{"cna":{"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"}]}],"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":["x_refsource_CONFIRM"]},{"url":"https://github.com/pnggroup/libpng/pull/824","name":"https://github.com/pnggroup/libpng/pull/824","tags":["x_refsource_MISC"]},{"url":"https://github.com/pnggroup/libpng/commit/23019269764e35ed8458e517f1897bd3c54820eb","name":"https://github.com/pnggroup/libpng/commit/23019269764e35ed8458e517f1897bd3c54820eb","tags":["x_refsource_MISC"]},{"url":"https://github.com/pnggroup/libpng/commit/7ea9eea884a2328cc7fdcb3c0c00246a50d90667","name":"https://github.com/pnggroup/libpng/commit/7ea9eea884a2328cc7fdcb3c0c00246a50d90667","tags":["x_refsource_MISC"]},{"url":"https://github.com/pnggroup/libpng/commit/a3a21443ed12bfa1ef46fa0d4fb2b74a0fa34a25","name":"https://github.com/pnggroup/libpng/commit/a3a21443ed12bfa1ef46fa0d4fb2b74a0fa34a25","tags":["x_refsource_MISC"]},{"url":"https://github.com/pnggroup/libpng/commit/c1b0318b393c90679e6fa5bc1d329fd5d5012ec1","name":"https://github.com/pnggroup/libpng/commit/c1b0318b393c90679e6fa5bc1d329fd5d5012ec1","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-416","lang":"en","description":"CWE-416: Use After Free","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-03-26T16:48:54.174Z"},"source":{"advisory":"GHSA-m4pc-p4q3-4c7j","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-03-31T00:00:00+00:00","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3","id":"CVE-2026-33416"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-04-01T03:55:17.603Z"}}]}}}