CVE-2026-33021High· 7.3▾ Twilightlibsixel 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 buffe…
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 40.2 · likelihood 0 · exploitation 0
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Exploit-prediction probability, daily snapshots since Jul 26.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
Last analysed / modified upstream
0.2%
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 dangling pointer. Any subsequent access to the original buffer by the caller constitutes a use-after-free, confirmed by AddressSanitizer. An attacker who controls incoming frames can trigger this bug repeatedly and predictably, resulting in a reliable crash with potential for code execution. This issue has been fixed in version 1.8.7-r1.
libsixel < 1.8.7-r1Upgrade past the affected range:
libsixel 1.8.7-r1Connected by shared product, vendor, weakness, or advisory.
CVE-2026-33023High· 7.8libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel
CVE-2026-33020High· 7.1libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel
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