Upstream information
Description
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 corrupt the heap of the victim process, resulting in a reliable crash and potential arbitrary code execution.This issue has been fixed in version 1.8.7-r1.
SUSE information
Overall state of this security issue: Analysis
This issue is currently rated as having important severity.
| CVSS detail | CNA (GitHub) | SUSE |
|---|---|---|
| Base Score | 7.1 | 7.1 |
| Vector | CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H | CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H |
| Attack Vector | Local | Local |
| Attack Complexity | Low | Low |
| Privileges Required | None | None |
| User Interaction | Required | Required |
| Scope | Unchanged | Unchanged |
| Confidentiality Impact | None | None |
| Integrity Impact | High | High |
| Availability Impact | High | High |
| CVSSv3 Version | 3.1 | 3.1 |
SUSE Timeline for this CVE
CVE page created: Wed Apr 15 02:01:01 2026CVE page last modified: Wed Apr 15 12:58:42 2026