What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-03-26 · updated 2026-06-17
• Weakness: CWE-125

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 products

• pnggroup libpng: from 1.6.36 before 1.6.56 — fixed in 1.6.56

How to fix

Upgrade to a fixed version: pnggroup libpng 1.6.56. Check the vendor advisory for mitigations.

References

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

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