CVE-2026-33636

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.

How to fix CVE-2026-33636

To remediate CVE-2026-33636, upgrade the affected package to a fixed version below.

• —upgrade to 1.6.56-r0 or later
• —upgrade to 1.6.37-3+deb11u3 or later

Is CVE-2026-33636 being exploited?

Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.

Affected packages (2)

• from 0, < 1.6.56-r0
• from 0, < 1.6.37-3+deb11u3

CVSS scores

References (2)

• ADVISORYsecurity.alpinelinux.org/vuln/CVE-2026-33636
• ADVISORYsecurity-tracker.debian.org/tracker/CVE-2026-33636