D-Link DIR-456U A1 Hardcoded Telnet Backdoor Credentials_CVE-2026-42376

{
    "lastseen": "",
    "description": "D-Link DIR-456U Hardware Revision A1 (End-of-Life, EOL) contains a hardcoded telnet backdoor. The device starts a telnet daemon at boot via /etc/init0.d/S80telnetd.sh with the username \"Alphanetworks\" and the static password \"whdrv01_dlob_dir456U\" read from /etc/config/image_sign. The custom telnetd binary accepts a -u user:password flag, and the custom login binary uses strcmp() to validate credentials. Successful authentication grants an unauthenticated attacker on the local network a root shell with full administrative control. The device has reached End-of-Life (EOL) and will not receive patches.",
    "published": "2026-05-04T16:03:59.473Z",
    "modified": "2026-05-04T16:03:59.473Z",
    "type": "cve",
    "title": "D-Link DIR-456U A1 Hardcoded Telnet Backdoor Credentials",
    "source": "securin",
    "references": "https://www.securin.io/zero-day/cve-2026-42376-hardcoded-telnet-backdoor-in-d-link-dir-456u-a1-end-of-life-",
    "id": "CVE-2026-42376",
    "bulletinFamily": "",
    "cwe": [
        "CWE-798"
    ],
    "cvelist": null,
    "sourceData": "D-Link DIR-456U Firmware A1",
    "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": {
        "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": "DIR-456U Firmware",
    "version": "A1",
    "vendor": "D-Link",
    "ai_description": "Hardcoded telnet backdoor credentials in D-Link DIR-456U A1 firmware",
    "ai_severity": "Critical",
    "ai_vendor": "D-Link",
    "ai_product": "DIR-456U",
    "ai_version": "A1",
    "ai_score": 9.8
}