CVE-2026-25646: LIBPNG has a heap buffer overflow in png_set_quantize

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-02-10 · updated 2026-08-11
Weakness: CWE-122

Description

LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. Prior to 1.6.55, an out-of-bounds read vulnerability exists in the png_set_quantize() API function. When the function is called with no histogram and the number of colors in the palette is more than twice the maximum supported by the user's display, certain palettes will cause the function to enter into an infinite loop that reads past the end of an internal heap-allocated buffer. The images that trigger this vulnerability are valid per the PNG specification. This vulnerability is fixed in 1.6.55.

Affected products

pnggroup libpng: before 1.6.55 — fixed in 1.6.55

How to fix

Upgrade to a fixed version: pnggroup libpng 1.6.55. Check the vendor advisory for mitigations.

References

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