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.
History

Thu, 14 May 2026 21:45:00 +0000

Type Values Removed Values Added
First Time appeared Saitoha
Saitoha libsixel
Vendors & Products Saitoha
Saitoha libsixel

Thu, 14 May 2026 20:15:00 +0000

Type Values Removed Values Added
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.
Title libsixel: integer overflow in parser
Weaknesses CWE-190
CWE-787
References
Metrics cvssV3_1

{'score': 7.1, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-05-14T20:02:32.034Z

Reserved: 2026-05-07T15:30:10.875Z

Link: CVE-2026-44637

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-05-14T20:17:08.847

Modified: 2026-05-14T21:21:10.620

Link: CVE-2026-44637

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-14T21:45:25Z