CVE-2026-33019

libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contain an integer overflow leading to an out-of-bounds heap read in the --crop option handling of img2sixel, where positive coordinates up to INT_MAX are accepted without overflow-safe bounds checking. In sixel_encoder_do_clip(), the expression clip_w + clip_x overflows to a large negative value when clip_x is INT_MAX, causing the bounds guard to be skipped entirely, and the unclamped coordinate is passed through sixel_frame_clip() to clip(), which computes a source pointer far beyond the image buffer and passes it to memmove(). An attacker supplying a specially crafted crop argument with any valid image can trigger an out-of-bounds read in the heap, resulting in a reliable crash and potential information disclosure. This issue has been fixed in version 1.8.7-r1.

• CWE-125
• CWE-190

• https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1Release Notes
• https://github.com/saitoha/libsixel/security/advisories/GHSA-c854-ffg9-g72cExploit, Vendor Advisory
• https://github.com/saitoha/libsixel/security/advisories/GHSA-c854-ffg9-g72cExploit, Vendor Advisory

Published

Apr 14, 2026

Last Modified

Jul 25, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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