{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-5855", "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10", "state": "PUBLISHED", "assignerShortName": "VulnCheck", "dateReserved": "2026-04-08T19:28:35.667Z", "datePublished": "2026-08-06T18:39:06.869Z", "dateUpdated": "2026-08-06T18:39:06.869Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10", "shortName": "VulnCheck", "dateUpdated": "2026-08-06T18:39:06.869Z"}, "title": "Contiki-NG LwM2M TLV Parser Out-of-Bounds Read via Unchecked Buffer Length in lwm2m_tlv_read", "datePublic": "2026-08-06T19:00:00.000Z", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-125", "description": "CWE-125 Out-of-bounds read", "type": "CWE"}]}], "affected": [{"vendor": "Contiki-NG", "product": "Contiki-NG", "versions": [{"status": "affected", "version": "0", "lessThan": "f1673b5766d4d4d514cefb8a0350f43653574997", "versionType": "custom"}], "defaultStatus": "affected"}], "descriptions": [{"lang": "en", "value": "Contiki-NG's LwM2M TLV parser lwm2m_tlv_read() in os/services/lwm2m/lwm2m-tlv.c ignores its caller-supplied buffer length argument and reads up to six bytes from the input buffer with no bounds check. The caller in lwm2m-engine.c iterates while there is at least one byte remaining, so a crafted CoAP WRITE to any LwM2M endpoint whose final TLV supplies exactly one byte triggers up to five out-of-bounds reads of heap memory adjacent to the CoAP input buffer, disclosing memory contents (including key material and peer addresses) through the parsed tlv->id, tlv->length, and tlv->value fields. Corrupted tlv_len derived from the out-of-bounds memory further corrupts the caller's parse offset. In LwM2M NoSec mode, the default for constrained devices, no authentication is required.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "Contiki-NG's LwM2M TLV parser lwm2m_tlv_read() in os/services/lwm2m/lwm2m-tlv.c ignores its caller-supplied buffer length argument and reads up to six bytes from the input buffer with no bounds check. The caller in lwm2m-engine.c iterates while there is at least one byte remaining, so a crafted CoAP WRITE to any LwM2M endpoint whose final TLV supplies exactly one byte triggers up to five out-of-bounds reads of heap memory adjacent to the CoAP input buffer, disclosing memory contents (including key material and peer addresses) through the parsed tlv->id, tlv->length, and tlv->value fields. Corrupted tlv_len derived from the out-of-bounds memory further corrupts the caller's parse offset. In LwM2M NoSec mode, the default for constrained devices, no authentication is required."}]}], "references": [{"url": "https://github.com/contiki-ng/contiki-ng", "tags": ["product"]}, {"url": "https://github.com/contiki-ng/contiki-ng/pull/3165", "tags": ["issue-tracking"]}, {"url": "https://github.com/contiki-ng/contiki-ng/commit/f1673b5766d4d4d514cefb8a0350f43653574997", "tags": ["patch"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV3_1": {"version": "3.1", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH", "baseSeverity": "HIGH", "baseScore": 7.5, "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}}, {"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "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": "HIGH", "baseScore": 8.7, "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"}}], "credits": [{"lang": "en", "value": "Kazuma Matsumoto, a security researcher at GMO Cybersecurity by IERAE, Inc.", "type": "reporter"}], "source": {"discovery": "UNKNOWN"}, "x_generator": {"engine": "vulncheck"}}}}

{}

{}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "[0,f1673b5766d4d4d514cefb8a0350f43653574997)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Contiki-NG", "source": "cna", "vendor": "Contiki-NG"}, "product": "contiki-ng", "vendor": "contiki-ng"}], "created": "2026-08-07T00:45:04.373115+00:00", "updated": "2026-08-07T01:15:04.954399+00:00", "vendors": ["contiki-ng", "contiki-ng$PRODUCT$contiki-ng"]}