{"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":"2026-08-14T16:50:26.324Z"},"containers":{"cna":{"providerMetadata":{"orgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","shortName":"VulnCheck","dateUpdated":"2026-08-14T16:50:26.324Z"},"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"}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:contiki-ng:contiki-ng:*:*:*:*:*:*:*:*"}]}]}],"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"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-07T16:19:49.994663Z","id":"CVE-2026-5855","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-08-07T16:19:59.210Z"}}]}}