{"id":"UBUNTU-CVE-2026-33416","details":"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-\u003etrans_alpha = info_ptr-\u003etrans_alpha` (256-byte buffer) and `png_set_PLTE` sets `info_ptr-\u003epalette = png_ptr-\u003epalette` (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.","modified":"2026-08-18T22:15:15.328703982Z","published":"2026-03-26T17:16:00Z","related":["USN-8251-1","USN-8639-1"],"upstream":["CVE-2026-33416"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-33416"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-33416"},{"type":"REPORT","url":"https://github.com/pnggroup/libpng/security/advisories/GHSA-m4pc-p4q3-4c7j"},{"type":"REPORT","url":"https://github.com/pnggroup/libpng/pull/824"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8251-1"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8639-1"}],"affected":[{"package":{"name":"libpng","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/libpng?arch=source&distro=esm-infra-legacy%2Ftrusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.2.50-1ubuntu2.14.04.3+esm2"}]}],"versions":["1.2.49-4ubuntu1","1.2.49-5ubuntu1","1.2.50-1ubuntu1","1.2.50-1ubuntu2","1.2.50-1ubuntu2.14.04.1","1.2.50-1ubuntu2.14.04.2","1.2.50-1ubuntu2.14.04.3","1.2.50-1ubuntu2.14.04.3+esm1"],"ecosystem_specific":{"availability":"Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro","binaries":[{"binary_version":"1.2.50-1ubuntu2.14.04.3+esm2","binary_name":"libpng12-0"},{"binary_name":"libpng3","binary_version":"1.2.50-1ubuntu2.14.04.3+esm2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33416.json"}},{"package":{"name":"libpng","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/libpng?arch=source&distro=esm-infra-legacy%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.2.54-1ubuntu1.1+esm3"}]}],"versions":["1.2.51-0ubuntu3","1.2.54-1","1.2.54-1ubuntu1","1.2.54-1ubuntu1.1","1.2.54-1ubuntu1.1+esm1","1.2.54-1ubuntu1.1+esm2"],"ecosystem_specific":{"availability":"Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro","binaries":[{"binary_name":"libpng12-0","binary_version":"1.2.54-1ubuntu1.1+esm3"},{"binary_name":"libpng3","binary_version":"1.2.54-1ubuntu1.1+esm3"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33416.json"}},{"package":{"name":"libpng1.6","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/libpng1.6?arch=source&distro=esm-apps-legacy%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.6.20-2ubuntu0.1~esm4"}]}],"versions":["1.6.20-2","1.6.20-2ubuntu0.1~esm1","1.6.20-2ubuntu0.1~esm2","1.6.20-2ubuntu0.1~esm3"],"ecosystem_specific":{"availability":"Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro","binaries":[{"binary_name":"libpng16-16","binary_version":"1.6.20-2ubuntu0.1~esm4"},{"binary_name":"libpng16-devtools","binary_version":"1.6.20-2ubuntu0.1~esm4"},{"binary_name":"libpng16-tools","binary_version":"1.6.20-2ubuntu0.1~esm4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33416.json"}},{"package":{"name":"libpng1.6","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/libpng1.6?arch=source&distro=esm-infra%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.6.34-1ubuntu0.18.04.2+esm3"}]}],"versions":["1.6.34-1","1.6.34-1ubuntu0.18.04.1","1.6.34-1ubuntu0.18.04.2","1.6.34-1ubuntu0.18.04.2+esm1","1.6.34-1ubuntu0.18.04.2+esm2"],"ecosystem_specific":{"binaries":[{"binary_name":"libpng-tools","binary_version":"1.6.34-1ubuntu0.18.04.2+esm3"},{"binary_name":"libpng16-16","binary_version":"1.6.34-1ubuntu0.18.04.2+esm3"}],"availability":"Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33416.json"}},{"package":{"name":"libpng1.6","ecosystem":"Ubuntu:Pro:20.04:LTS","purl":"pkg:deb/ubuntu/libpng1.6?arch=source&distro=esm-infra%2Ffocal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.6.37-2ubuntu0.1~esm3"}]}],"versions":["1.6.37-1","1.6.37-2","1.6.37-2ubuntu0.1~esm1","1.6.37-2ubuntu0.1~esm2"],"ecosystem_specific":{"binaries":[{"binary_version":"1.6.37-2ubuntu0.1~esm3","binary_name":"libpng-tools"},{"binary_version":"1.6.37-2ubuntu0.1~esm3","binary_name":"libpng16-16"}],"availability":"Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33416.json"}},{"package":{"name":"libpng1.6","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/libpng1.6?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.6.37-3ubuntu0.5"}]}],"versions":["1.6.37-3build4","1.6.37-3build5","1.6.37-3ubuntu0.1","1.6.37-3ubuntu0.3","1.6.37-3ubuntu0.4"],"ecosystem_specific":{"availability":"No subscription required","binaries":[{"binary_version":"1.6.37-3ubuntu0.5","binary_name":"libpng-tools"},{"binary_name":"libpng16-16","binary_version":"1.6.37-3ubuntu0.5"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33416.json"}},{"package":{"name":"libpng1.6","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/libpng1.6?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.6.43-5ubuntu0.6"}]}],"versions":["1.6.40-1","1.6.40-2","1.6.40-3","1.6.42-1","1.6.43-1","1.6.43-3","1.6.43-5build1","1.6.43-5ubuntu0.1","1.6.43-5ubuntu0.3","1.6.43-5ubuntu0.4","1.6.43-5ubuntu0.5"],"ecosystem_specific":{"availability":"No subscription required","binaries":[{"binary_name":"libpng-tools","binary_version":"1.6.43-5ubuntu0.6"},{"binary_name":"libpng16-16t64","binary_version":"1.6.43-5ubuntu0.6"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33416.json"}},{"package":{"name":"libpng1.6","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/libpng1.6?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.6.50-1ubuntu0.5"}]}],"versions":["1.6.47-1.1","1.6.48-1","1.6.49-1~exp1","1.6.50-1~exp1","1.6.50-1","1.6.50-1ubuntu0.1","1.6.50-1ubuntu0.3","1.6.50-1ubuntu0.4"],"ecosystem_specific":{"binaries":[{"binary_name":"libpng-tools","binary_version":"1.6.50-1ubuntu0.5"},{"binary_name":"libpng16-16t64","binary_version":"1.6.50-1ubuntu0.5"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33416.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H"},{"type":"Ubuntu","score":"medium"}]}