cvedb.io
CVE-2026-33020
HIGH · CVSS 7.1
EPSS exploitation probability: 0%
Published 2026-04-14T22:16:30.543 · Last modified 2026-06-17T10:36:47.553

Summary

libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contain an integer overflow which leads to a heap buffer overflow via sixel_frame_convert_to_rgb888() in frame.c, where allocation size and pointer offset computations for palettised images (PAL1, PAL2, PAL4) are performed using int arithmetic before casting to size_t. For images whose pixel count exceeds INT_MAX / 4, the overflow produces an undersized heap allocation for the conversion buffer and a negative pointer offset for the normalization sub-buffer, after which sixel_helper_normalize_pixelformat() writes the full image data starting from the invalid pointer, causing massive heap corruption confirmed by ASAN. An attacker providing a specially crafted large palettised PNG can corru

Affected products

saitoha — libsixel

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References

This product uses data from the NVD API but is not endorsed or certified by the NVD. Informational only; not professional security advice.