What is CVE-2026-33021?

CVE-2026-33021 is a high-severity vulnerability in Saitoha Libsixel, classified under Use After Free. CVSS score: 7.3/10. Published 2026-04-14.

How severe is CVE-2026-33021?

High severity. CVSS v3 base score is 7.3 out of 10.

Use After Free in Saitoha Libsixel

CVE-2026-33021

libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contain a use-after-free vulnerability in sixel_encoder_encode_bytes() because sixel_frame_init() stores the caller-owned pixel buffer…

Vulnerability class: Use-After-Free

EPSS: 0.000 (0.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.3 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H.

Affected products

Saitoha Libsixel — versions < 1.8.7-r1

Weakness classification (CWE)

CWE-416 — Use After Free

References

https://github.com/saitoha/libsixel/security/advisories/GHSA-j6m5-2cc7-3whc (x_refsource_CONFIRM)
https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1 (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-33021?: CVE-2026-33021 is a high-severity vulnerability in Saitoha Libsixel, classified under Use After Free. CVSS score: 7.3/10. Published 2026-04-14.
How severe is CVE-2026-33021?: High severity. CVSS v3 base score is 7.3 out of 10.