libsixel: Use-after-free in sixel_encoder_encode_bytes()_CVE-2026-33021

{
    "lastseen": "",
    "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.",
    "published": "2026-04-14T21:57:22.817Z",
    "modified": "2026-04-14T21:57:22.817Z",
    "type": "cve",
    "title": "libsixel: Use-after-free in sixel_encoder_encode_bytes()",
    "source": "GitHub_M",
    "references": "https://github.com/saitoha/libsixel/security/advisories/GHSA-j6m5-2cc7-3whc\nhttps://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1",
    "id": "CVE-2026-33021",
    "bulletinFamily": "",
    "cwe": [
        "CWE-416"
    ],
    "cvelist": null,
    "sourceData": "saitoha libsixel < 1.8.7-r1",
    "sourceHref": "",
    "cvss": {
        "score": 7.3,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "libsixel",
    "version": "< 1.8.7-r1",
    "vendor": "saitoha",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}