LibVNCClient Tight Gradient decoding allows malicious server-triggered heap/stack OOB writes_CVE-2026-44988

{
    "lastseen": "",
    "description": "LibVNCClient is a library for easy implementation of a VNC client. In 0.9.15 and earlier, LibVNCClient's Tight encoding decoder uses fixed-size 2048-pixel scratch buffers for the Gradient filter, but it does not reject Tight rectangles whose width is larger than 2048 pixels. A malicious VNC server can send a crafted FramebufferUpdate rectangle using Tight encoding with NoZlib | ExplicitFilter and the Gradient filter. When a LibVNCClient-based client connects, the client processes the server-controlled rectangle width and writes beyond fixed-size Gradient buffers. This vulnerability is fixed with commit 5b270544b85233668b98161323297d418a8f5fd1.",
    "published": "2026-05-27T14:26:50.063Z",
    "modified": "2026-05-27T14:26:50.063Z",
    "type": "cve",
    "title": "LibVNCClient Tight Gradient decoding allows malicious server-triggered heap/stack OOB writes",
    "source": "GitHub_M",
    "references": "https://github.com/LibVNC/libvncserver/security/advisories/GHSA-jcc5-8wj4-7c58\nhttps://github.com/LibVNC/libvncserver/commit/5b270544b85233668b98161323297d418a8f5fd1",
    "id": "CVE-2026-44988",
    "bulletinFamily": "",
    "cwe": [
        "CWE-787"
    ],
    "cvelist": null,
    "sourceData": "LibVNC libvncserver <= 0.9.15",
    "sourceHref": "",
    "cvss": {
        "score": 8.8,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/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": "",
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            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "libvncserver",
    "version": "<= 0.9.15",
    "vendor": "LibVNC",
    "ai_description": "Malicious VNC server can trigger heap/stack OOB writes via crafted FramebufferUpdate rectangle",
    "ai_severity": "High",
    "ai_vendor": "LibVNC",
    "ai_product": "libvncserver",
    "ai_version": "<= 0.9.15",
    "ai_score": 8.8
}