The BACnet Protocol Stack library has an Off-by-one Stack-based Buffer Overflow in tokenizer_string_CVE-2026-21870

{
    "lastseen": "",
    "description": "BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services. In 1.4.2, 1.5.0.rc2, and earlier, an off-by-one stack-based buffer overflow in the ubasic interpreter causes a crash (SIGABRT) when processing string literals longer than the buffer limit. The tokenizer_string function in src/bacnet/basic/program/ubasic/tokenizer.c incorrectly handles null termination for maximum-length strings. It writes a null byte to dest[40] when the buffer size is only 40 (indices 0-39), triggering a stack overflow.",
    "published": "2026-02-13T17:58:37.205Z",
    "modified": "2026-02-13T18:19:36.183Z",
    "type": "cve",
    "title": "The BACnet Protocol Stack library has an Off-by-one Stack-based Buffer Overflow in tokenizer_string",
    "source": "GitHub_M",
    "references": "https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-pc83-wp6w-93mx\nhttps://github.com/bacnet-stack/bacnet-stack/pull/1196\nhttps://github.com/bacnet-stack/bacnet-stack/commit/4e1176394a5ae50d2fd0b5790d9bff806dc08465",
    "id": "CVE-2026-21870",
    "bulletinFamily": "",
    "cwe": [
        "CWE-193"
    ],
    "cvelist": null,
    "sourceData": "bacnet-stack bacnet-stack <= 1.4.2\nbacnet-stack bacnet-stack >= 1.5.0.rc1, <= 1.5.0.rc2",
    "sourceHref": "",
    "cvss": {
        "score": 5.5,
        "severity": "MEDIUM",
        "vector": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
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        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
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        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "bacnet-stack",
    "version": "<= 1.4.2",
    "vendor": "bacnet-stack",
    "ai_description": "",
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    "ai_score": 0
}