arduino-esp32: Stack buffer overflow in WebServer multipart boundary parsing leads to remote crash potential RCE_CVE-2026-42854

{
    "lastseen": "",
    "description": "arduino-esp32 is an Arduino core for the ESP32, ESP32-S2, ESP32-S3, ESP32-C3, ESP32-C6 and ESP32-H2 microcontrollers. Prior to 3.3.8, the WebServer multipart form parser in arduino-esp32 allocates a Variable Length Array (VLA) on the stack whose size is derived from an attacker-controlled HTTP header field (Content-Type: multipart/form-data; boundary=...) without enforcing any length limit. Sending a boundary string longer than ~8000 characters overflows the 8192-byte task stack of the loopTask, causing a crash and potential remote code execution. This vulnerability is fixed in 3.3.8.",
    "published": "2026-05-12T21:56:33.437Z",
    "modified": "2026-05-12T21:56:33.437Z",
    "type": "cve",
    "title": "arduino-esp32: Stack buffer overflow in WebServer multipart boundary parsing leads to remote crash potential RCE",
    "source": "GitHub_M",
    "references": "https://github.com/espressif/arduino-esp32/security/advisories/GHSA-8cmm-3887-r32j",
    "id": "CVE-2026-42854",
    "bulletinFamily": "",
    "cwe": [
        "CWE-121"
    ],
    "cvelist": null,
    "sourceData": "espressif arduino-esp32 < 3.3.8",
    "sourceHref": "",
    "cvss": {
        "score": 9.8,
        "severity": "CRITICAL",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
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        "baseScore": 0,
        "baseSeverity": "",
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        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
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    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "arduino-esp32",
    "version": "< 3.3.8",
    "vendor": "espressif",
    "ai_description": "",
    "ai_severity": "",
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    "ai_score": 0
}