Vulnerability Description
libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, a signed integer overflow in the SIXEL parser's image-buffer doubling loop can lead to an out-of-bounds heap write in sixel_decode_raw_impl. context->pos_x grows by repeat_count on every sixel character with no upper bound check. Once pos_x approaches INT_MAX, the expression "pos_x + repeat_count" used to size the image buffer overflows signed int. Depending on how the overflow wraps, the resize check that should reject oversized buffers can be bypassed, after which a subsequent write computes a large attacker-influenced offset into image->data and writes past the allocation. Reachable from any caller that decodes attacker-supplied SIXEL data, including img2sixel. This vulnerability is fixed in 1.8.7-r2.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Saitoha | Libsixel | >= 0.11.0, < 1.8.7-r2 |
Related Weaknesses (CWE)
References
- https://github.com/saitoha/libsixel/security/advisories/GHSA-9jm7-77gr-qghvExploitVendor Advisory
- https://github.com/saitoha/libsixel/security/advisories/GHSA-9jm7-77gr-qghvExploitVendor Advisory
FAQ
What is CVE-2026-44637?
CVE-2026-44637 is a vulnerability with a CVSS score of 7.1 (HIGH). libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, a signed integer overflow in the SIXEL parser's image-buffer doubling loop can lead to an out-of-bound...
How severe is CVE-2026-44637?
CVE-2026-44637 has been rated HIGH with a CVSS base score of 7.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-44637?
Check the references section above for vendor advisories and patch information. Affected products include: Saitoha Libsixel.