Contiki-NG LwM2M TLV Parser Out-of-Bounds Read via Unchecked Buffer Length in lwm2m_tlv_read
Summary
| CVE | CVE-2026-5855 |
|---|---|
| State | PUBLISHED |
| Assigner | VulnCheck |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-08-06 22:18:10 UTC |
| Updated | 2026-08-07 17:17:05 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 8.7 HIGH from [email protected]
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS: 0.005370000 probability, percentile 0.423140000 (date 2026-08-07)
Problem Types: CWE-125 | CWE-125 CWE-125 Out-of-bounds read
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 8.7 | HIGH | 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/E:X/C... |
| 4.0 | CNA | CVSS | 8.7 | HIGH | 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 |
| 3.1 | [email protected] | Secondary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | CNA | CVSS | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
CVSS v4.0 Breakdown
Attack Vector
NetworkAttack Complexity
LowAttack Requirements
NonePrivileges Required
NoneUser Interaction
NoneConfidentiality
NoneIntegrity
NoneAvailability
HighSub Conf.
NoneSub Integrity
NoneSub Availability
NoneCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
NoneAvailability
HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Contiki-NG | Contiki-NG | affected f1673b5766d4d4d514cefb8a0350f43653574997 custom | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/contiki-ng/contiki-ng | [email protected] | github.com | |
| github.com/contiki-ng/contiki-ng/commit/f1673b5766d4d4d514cefb8a0350f436... | [email protected] | github.com | |
| github.com/contiki-ng/contiki-ng/pull/3165 | [email protected] | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Kazuma Matsumoto, a security researcher at GMO Cybersecurity by IERAE, Inc. (en)
There are currently no legacy QID mappings associated with this CVE.