CVE-2026-44636
HighSummary
The libsixel library has a heap buffer overflow due to incorrect allocation size calculation in the sixel_encode_highcolor function. This issue affects versions from 1.8.7-r1 to 1.8.7-r2, where the lack of an upper bound for width and height allows for potential memory overwrites.
Risk Assessment
An attacker could exploit this vulnerability to overwrite memory, potentially leading to unauthorized data access or execution of malicious code. Organizations should be aware of the risks associated with using vulnerable versions of the library.
Recommendation
It is recommended to update the libsixel library to version 1.8.7-r2 or later to mitigate this vulnerability. Additionally, implementing validation checks for width and height in applications using this library is advisable.
Other vulnerabilities in libsixel
See all- CVE-2026-44637High
The libsixel library has a signed integer overflow in the image-buffer doubling loop of the SIXEL parser, which can lead to an out-of-bounds heap write. This issue affects versions up to 1.8.7-r1 and is fixed in version 1.8.7-r2.
- CVE-2026-33023High
In libsixel versions 1.8.7 and prior, built with --with-gdk-pixbuf2, a use-after-free vulnerability exists in load_with_gdkpixbuf(). The cleanup path manually frees the sixel_frame_t object without consulting the reference count, leading to a dangling pointer. An attacker can supply a crafted image, potentially causing information disclosure, memory corruption, or code execution.
Original NVD description (English source)
libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, signed integer overflow in sixel_encode_highcolor's allocation size calculation can lead to a heap buffer overflow. The public sixel_encode entry point validates only that width and height are greater than zero, with no upper bound. width and height are multiplied as plain int when computing the allocation size for paletted_pixels and normalized_pixels. Any caller that asks libsixel to encode a pixel buffer with width times height greater than INT_MAX (about 2.15 billion) will hit a wrapped allocation size; under the right wrap, the malloc succeeds with a buffer much smaller than the encoder expects, and the encoder writes past the end of the heap allocation. This vulnerability is fixed in 1.8.7-r2.