Upstream information
Description
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.SUSE information
Overall state of this security issue: Does not affect SUSE products
This issue is currently rated as having important severity.
| CVSS detail | CNA (GitHub) | National Vulnerability Database | SUSE |
|---|---|---|---|
| Base Score | 7.4 | 7.8 | 7.4 |
| Vector | CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H | CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H |
| Attack Vector | Local | Local | Local |
| Attack Complexity | High | Low | High |
| Privileges Required | None | Low | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality Impact | High | High | High |
| Integrity Impact | High | High | High |
| Availability Impact | High | High | High |
| CVSSv3 Version | 3.1 | 3.1 | 3.1 |
SUSE Timeline for this CVE
CVE page created: Fri May 15 00:08:40 2026CVE page last modified: Fri May 15 21:30:39 2026