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CVE-2026-33416 Detail

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.


Metrics

NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

References to Advisories, Solutions, and Tools

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URL Source(s) Tag(s)
https://github.com/pnggroup/libpng/commit/23019269764e35ed8458e517f1897bd3c54820eb GitHub, Inc.
https://github.com/pnggroup/libpng/commit/7ea9eea884a2328cc7fdcb3c0c00246a50d90667 GitHub, Inc.
https://github.com/pnggroup/libpng/commit/a3a21443ed12bfa1ef46fa0d4fb2b74a0fa34a25 GitHub, Inc.
https://github.com/pnggroup/libpng/commit/c1b0318b393c90679e6fa5bc1d329fd5d5012ec1 GitHub, Inc.
https://github.com/pnggroup/libpng/pull/824 GitHub, Inc.
https://github.com/pnggroup/libpng/security/advisories/GHSA-m4pc-p4q3-4c7j GitHub, Inc.

Weakness Enumeration

CWE-ID CWE Name Source
CWE-416 Use After Free GitHub, Inc.  

Change History

1 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2026-33416
NVD Published Date:
03/26/2026
NVD Last Modified:
03/26/2026
Source:
GitHub, Inc.