Vulnerability 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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Libpng | Libpng | >= 1.6.36, < 1.6.56 |
Related Weaknesses (CWE)
References
- https://github.com/pnggroup/libpng/commit/7734cda20cf1236aef60f3bbd2267c97bbb408Patch
- https://github.com/pnggroup/libpng/commit/aba9f18eba870d14fb52c5ba5d73451349e339Patch
- https://github.com/pnggroup/libpng/security/advisories/GHSA-wjr5-c57x-95m2Vendor AdvisoryPatch
FAQ
What is CVE-2026-33636?
CVE-2026-33636 is a vulnerability with a CVSS score of 7.6 (HIGH). 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...
How severe is CVE-2026-33636?
CVE-2026-33636 has been rated HIGH with a CVSS base score of 7.6/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-33636?
Check the references section above for vendor advisories and patch information. Affected products include: Libpng Libpng.