{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-66747", "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10", "state": "PUBLISHED", "assignerShortName": "VulnCheck", "dateReserved": "2026-07-27T16:27:47.648Z", "datePublished": "2026-08-05T10:50:45.576Z", "dateUpdated": "2026-08-05T14:20:12.478Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10", "shortName": "VulnCheck", "dateUpdated": "2026-08-05T10:55:20.206Z"}, "title": "ENDLESSDOORS: Zbtlink Router rctl/kworker Phone-Home Root Implant", "datePublic": "2026-08-05T00:00:00.000Z", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-506", "description": "CWE-506 Embedded Malicious Code", "type": "CWE"}]}], "affected": [{"vendor": "Zbtlink", "product": "CPE2801 Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "22.10.09", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:cpe2801_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "WE1026-5G-WD Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "21.04.07", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:we1026-5g-wd_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "WE1326 Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "22.02.18_1", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:we1326_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "WE2007 Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "23.08.12", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:we2007_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "WE2008-DSIM Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "23.08.11", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:we2008-dsim_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "WE2416 Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "21.03.22_1", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:we2416_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "WE3326 Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "20.09.30", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:we3326_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "WE5927 Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "22.08.10", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:we5927_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "WE5931 Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "22.05.31", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:we5931_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "WE5931AC Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "22.05.31", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:we5931ac_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "WE826-T3-DSIM Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "21.12.21", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:we826-t3-dsim_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "WG108 Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "21.08.06_1", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": 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"custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:wg1608-dsim_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "WG2105 Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "22.05.30", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:wg2105_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "WG2107 Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "22.09.08", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:wg2107_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "WG3526 Firmware", "platforms": ["MIPS", "ARM"], "versions": [{"status": "affected", "version": "22.11.01", "versionType": "custom"}], "defaultStatus": "unaffected", "cpes": ["cpe:2.3:o:zbtlink:wg3526_firmware:*:*:*:*:*:*:*:*"]}, {"vendor": "Zbtlink", "product": "ZBT-Z8102AX-2SIM Firmware", "platforms": ["ARM"], "versions": 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It is the open-source ycsunjane/rctl tool built in as an OpenWrt package (librctl.so), started at boot and run as root under the process name kworker to blend in with the kernel's [kworker/*] threads. It opens no listening port; it phones home over cleartext TCP to a hardcoded command-and-control server (command channel 7000, interactive-shell callback 7001) with no authentication and no transport encryption, re-attempting contact roughly every 35 seconds. Its command handler passes any received string to popen() as uid=0, and a reserved rctlbash command returns an interactive root shell. Because the channel is unauthenticated and cleartext, control is not limited to whoever planted it: any party that answers at the C2 address, occupies the network path (DNS or route hijack), or acquires the hardcoded fallback domain obtains unauthenticated remote code execution as root.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "<p>Zbtlink router firmware ships an embedded remote-control implant, ENDLESSDOORS, present in every published build across the product line. It is the open-source ycsunjane/rctl tool built in as an OpenWrt package (librctl.so), started at boot and run as root under the process name kworker to blend in with the kernel's [kworker/*] threads. It opens no listening port; it phones home over cleartext TCP to a hardcoded command-and-control server (command channel 7000, interactive-shell callback 7001) with no authentication and no transport encryption, re-attempting contact roughly every 35 seconds. Its command handler passes any received string to popen() as uid=0, and a reserved rctlbash command returns an interactive root shell. Because the channel is unauthenticated and cleartext, control is not limited to whoever planted it: any party that answers at the C2 address, occupies the network path (DNS or route hijack), or acquires the hardcoded fallback domain obtains unauthenticated remote code execution as root.</p>"}]}], "references": [{"url": "https://www.vulncheck.com/blog/zbt-endlessdoors", "name": "VulnCheck Research Blog", "tags": ["technical-description", "exploit"]}, {"url": "https://www.zbtlink.com/pages/zbt-router-firmware-download", "name": "Vendor Firmware Download Page", "tags": ["product"]}, {"url": "https://github.com/ycsunjane/rctl", "name": "Upstream Open Source rctl"}, {"url": "https://www.vulncheck.com/advisories/zbt-endlessdoors", "name": "VulnCheck Advisory", "tags": ["third-party-advisory"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "HIGH", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "subIntegrityImpact": "NONE", "vulnAvailabilityImpact": "HIGH", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "version": "4.0", "baseSeverity": "CRITICAL", "baseScore": 9.3, "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"}}, {"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV3_1": {"version": "3.1", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH", "baseSeverity": "CRITICAL", "baseScore": 9.8, "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"}}], "credits": [{"lang": "en", "value": "Jacob Baines of VulnCheck", "type": "finder"}], "source": {"discovery": "UNKNOWN"}, "x_generator": {"engine": "vulncheck"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-08-05T14:19:25.533200Z", "id": "CVE-2026-66747", "options": [{"Exploitation": "poc"}, {"Automatable": "yes"}, {"Technical Impact": "total"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-08-05T14:20:12.478Z"}}]}}

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