← Vulnerability feed

Vulnerability record · CVE-2026-44636 · published 14 May 2026

CVE-2026-44636: Saitoha libsixel heap-based buffer overflow vulnerability

SSaitoha · Libsixel

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.

7.8 CVSS 3.1 High EPSS 0.14% · top 97.3% CWE-122 · Heap-based buffer overflowCWE-190 · Integer overflow
7.8CVSS 3.1 base score
0.14%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

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:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/saitoha/libsixel/security/advisories/GHSA-hx93-w8p2-ffh5 Vendor Advisory
https://github.com/saitoha/libsixel/security/advisories/GHSA-hx93-w8p2-ffh5 Vendor Advisory

Track CVE-2026-44636 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2019-19637Saitoha libsixel integer overflow vulnerabilityAn issue was discovered in libsixel 1.8.2. There is an integer overflow in the function sixel_decode_raw_impl at fromsixel.c.EPSS 1.2%9.8CVE-2019-19638Saitoha libsixel integer overflow vulnerabilityAn issue was discovered in libsixel 1.8.2. There is a heap-based buffer overflow in the function load_pnm at frompnm.c, due to an integer overflow.EPSS 1.2%9.8CVE-2019-19635Saitoha libsixel out-of-bounds write vulnerabilityAn issue was discovered in libsixel 1.8.2. There is a heap-based buffer overflow in the function sixel_decode_raw_impl at fromsixel.c.EPSS 1.2%9.8CVE-2019-19636Saitoha libsixel integer overflow vulnerabilityAn issue was discovered in libsixel 1.8.2. There is an integer overflow in the function sixel_encode_body at tosixel.c.EPSS 1.2%8.8CVE-2022-27044Saitoha libsixel out-of-bounds write vulnerabilitylibsixel 1.8.6 is affected by Buffer Overflow in libsixel/src/quant.c:876.EPSS 1.0%8.8CVE-2022-27046Saitoha libsixel use after free vulnerabilitylibsixel 1.8.6 suffers from a Heap Use After Free vulnerability in in libsixel/src/dither.c:388.EPSS 1.0%8.8CVE-2020-21547Saitoha libsixel out-of-bounds write vulnerabilityLibsixel 1.8.2 contains a heap-based buffer overflow in the dither_func_fs function in tosixel.c.EPSS 1.1%8.8CVE-2020-21548Saitoha libsixel out-of-bounds write vulnerabilityLibsixel 1.8.3 contains a heap-based buffer overflow in the sixel_encode_highcolor function in tosixel.c.EPSS 1.1%

Source: NIST National Vulnerability Database (record CVE-2026-44636), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.