Vulnerability · Published Apr 14, 2026 · Assigned by GitHub_M
CVE-2026-33019libsixel: Integer overflow leads to Out-of-bounds Read in img2sixel
High 7.1
In plain English
A high-severity out-of-bounds read in libsixel from saitoha. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 17% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | libsixel | no fix listed | DEBIAN-CVE-2026-33019 |
| Debian:13 | libsixel | no fix listed | DEBIAN-CVE-2026-33019 |
| Debian:14 | libsixel | 1:1.8.7-r2-1 | DEBIAN-CVE-2026-33019 |
| Ubuntu:22.04:LTS | libsixel | no fix listed | UBUNTU-CVE-2026-33019 |
| Ubuntu:24.04:LTS | libsixel | no fix listed | UBUNTU-CVE-2026-33019 |
| Ubuntu:25.10 | libsixel | no fix listed | UBUNTU-CVE-2026-33019 |
| Ubuntu:26.04:LTS | libsixel | no fix listed | UBUNTU-CVE-2026-33019 |
| Ubuntu:26.10 | libsixel | no fix listed | UBUNTU-CVE-2026-33019 |
Affected products (as reported)
Weakness: CWE-125, CWE-190 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
References
- https://github.com/saitoha/libsixel/security/advisories/GHSA-c854-ffg9-g72c x_refsource_CONFIRM
- https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1 x_refsource_MISC