CVE-2026-33636: libpng Out-of-bounds Read

Vulnerability summary

CVE-2026-33636 is a high (CVSS 7.6) Out-of-bounds Read vulnerability in libpng. EPSS estimates a 0.36% chance of exploitation in the next 30 days, higher than 28.6% of scored vulnerabilities.

Timeline

1. 26-03-2026
   PublishedVulnerability first disclosed.
2. 26-03-2026
   Last modifiedVulnerability information updated.

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.

• CWE-125Out-of-bounds ReadThe product reads data past the end, or before the beginning, of the intended buffer.
• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.