CVE-2026-33021
7.3 · HIGHOverview
CVE-2026-33021 is a high-severity vulnerability affecting saitoha libsixel. It was published on April 14, 2026 and has a CVSS 3.1 base score of 7.3 (HIGH).
This vulnerability has a CVSS 3.1 base score of 7.3, 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 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.
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-2026-33021?
CVE-2026-33021 is a high-severity vulnerability affecting saitoha libsixel. It was published on April 14, 2026 and has a CVSS 3.1 base score of 7.3 (HIGH).
How severe is CVE-2026-33021?
This vulnerability has a CVSS 3.1 base score of 7.3, 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-2026-33021?
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-2026-33021?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-33021 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.
How CyberStrike Helps
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