CVE-2026-33636LIBPNG has ARM NEON Palette Expansion Out-of-Bounds Read on AArch64

Official description

LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. In versions 1.6.36 through 1.6.55, an out-of-bounds read and write exists in libpng's ARM/AArch64 Neon-optimized palette expansion path. When expanding 8-bit paletted rows to RGB or RGBA, the Neon loop processes a final partial chunk without verifying that enough input pixels remain. Because the implementation works backward from the end of the row, the final iteration dereferences pointers before the start of the row buffer (OOB read) and writes expanded pixel data to the same underflowed positions (OOB write). This is reachable via normal decoding of attacker-controlled PNG input if Neon is enabled. Version 1.6.56 fixes the issue.

Affected packages & fixed versions

Affected products (as reported)

References

• https://github.com/pnggroup/libpng/security/advisories/GHSA-wjr5-c57x-95m2 x_refsource_CONFIRM
• https://github.com/pnggroup/libpng/commit/7734cda20cf1236aef60f3bbd2267c97bbb40869 x_refsource_MISC
• https://github.com/pnggroup/libpng/commit/aba9f18eba870d14fb52c5ba5d73451349e339c3 x_refsource_MISC