Vulnerability Description
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.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/contiki-ng/contiki-ng
- https://github.com/contiki-ng/contiki-ng/commit/f1673b5766d4d4d514cefb8a0350f436
- https://github.com/contiki-ng/contiki-ng/pull/3165
FAQ
What is CVE-2026-5855?
CVE-2026-5855 is a vulnerability with a CVSS score of 7.5 (HIGH). 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....
How severe is CVE-2026-5855?
CVE-2026-5855 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-5855?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.