CVE-2026-33021 — Use After Free in Libsixel

CWE-416 — Use After FreeCWE-825 — Expired Pointer Dereference5 documents4 sources
Severity
7.3HIGHNVD
EPSS
0.0%
top 97.35%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
1
Saitoha Libsixel
Timeline
PublishedApr 14
Latest updateApr 15

Description

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 pointer directly in frame->pixels without making a defensive copy. When a resize operation is triggered, sixel_frame_convert_to_rgb888() unconditionally frees this caller-owned buffer and replaces it with a new internal allocation, leaving the caller with a dan…

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:HExploitability: 2.5 | Impact: 4.7

Affected Packages1 packages

▶CVEListV5saitoha/libsixel< 1.8.7-r1

🔴Vulnerability Details

1
CVEList
libsixel: Use-after-free in sixel_encoder_encode_bytes()↗2026-04-14
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📋Vendor Advisories

1
Red Hat
libsixel: libsixel: Use-after-free vulnerability allows for potential code execution via premature pixel buffer freeing.↗2026-04-14
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💬Community

2
Bugzilla
CVE-2026-33021 libsixel: libsixel: Use-after-free vulnerability allows for potential code execution via premature pixel buffer freeing. [fedora-all]↗2026-04-15
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Bugzilla
CVE-2026-33021 libsixel: libsixel: Use-after-free vulnerability allows for potential code execution via premature pixel buffer freeing.↗2026-04-14
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CVE-2026-33021 — Use After Free in Saitoha Libsixel | cvebase