Vulnerability Description
libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, signed integer overflow in sixel_encode_highcolor's allocation size calculation can lead to a heap buffer overflow. The public sixel_encode entry point validates only that width and height are greater than zero, with no upper bound. width and height are multiplied as plain int when computing the allocation size for paletted_pixels and normalized_pixels. Any caller that asks libsixel to encode a pixel buffer with width times height greater than INT_MAX (about 2.15 billion) will hit a wrapped allocation size; under the right wrap, the malloc succeeds with a buffer much smaller than the encoder expects, and the encoder writes past the end of the heap allocation. This vulnerability is fixed in 1.8.7-r2.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Saitoha | Libsixel | >= 1.4.4, < 1.8.7-r2 |
Related Weaknesses (CWE)
References
- https://github.com/saitoha/libsixel/security/advisories/GHSA-hx93-w8p2-ffh5Vendor Advisory
- https://github.com/saitoha/libsixel/security/advisories/GHSA-hx93-w8p2-ffh5Vendor Advisory
FAQ
What is CVE-2026-44636?
CVE-2026-44636 is a vulnerability with a CVSS score of 7.4 (HIGH). libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, signed integer overflow in sixel_encode_highcolor's allocation size calculation can lead to a heap buf...
How severe is CVE-2026-44636?
CVE-2026-44636 has been rated HIGH with a CVSS base score of 7.4/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-44636?
Check the references section above for vendor advisories and patch information. Affected products include: Saitoha Libsixel.