Out-of-bounds Read in Saitoha Libsixel
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.1 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H.
EPSS exploit prediction
EPSS: 0.002 (9.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 9th percentile — 9.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.002 · change: -0.001
Affected products
- Saitoha Libsixel — versions < 1.8.7-r1
Weakness classification (CWE)
References
- github.com/saitoha/libsixel/security/advisories/GHSA-c854-ffg9-g72c (Exploit, Vendor Advisory)
- github.com/saitoha/libsixel/releases/tag/v1.8.7-r1 (Release Notes)
Frequently asked questions
- What is CVE-2026-33019?
- CVE-2026-33019 is a high-severity vulnerability in Saitoha Libsixel, classified under Out-of-bounds Read. CVSS score: 7.1/10. Published 2026-04-14.
- How severe is CVE-2026-33019?
- High severity. CVSS v3 base score is 7.1 out of 10.