Handler on Duty: Guy Bruneau
Threat Level: green
| Published | 2026-04-14 23:16:27 |
|---|---|
| Last Modified | 2026-04-14 23:16:27 |
| AKA | CVE-2026-33021 |
| Summary | 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. |
| Access Vector | Local | Adjacent | Network |
|---|---|---|---|
| Access Complexity | Low | Medium | High |
| Authentication | None | Single | Multiple |
| Confidentiality | None | Partial | Complete |
| Integrity | None | Partial | Complete |
| Availability | None | Partial | Complete |