CVE-2026-33020
7.1 · HIGHOverview
CVE-2026-33020 is a high-severity vulnerability affecting saitoha libsixel. It was published on April 14, 2026 and has a CVSS 3.1 base score of 7.1 (HIGH).
This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It requires local or adjacent network access to exploit. No authentication or special privileges are required for exploitation.
Technical 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.
Remediation
Check the references section for vendor advisories and patches from saitoha. Update libsixel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| saitoha | libsixel | >= 0, < 1.8.7-r1 | Affected |
Frequently Asked Questions
What is CVE-2026-33020?
CVE-2026-33020 is a high-severity vulnerability affecting saitoha libsixel. It was published on April 14, 2026 and has a CVSS 3.1 base score of 7.1 (HIGH).
How severe is CVE-2026-33020?
This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It requires local or adjacent network access to exploit. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-33020?
Check the references section for vendor advisories and patches from saitoha. Update libsixel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-33020?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-33020 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
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