---
cve: "CVE-2026-5855"
severity: "HIGH"
cvss: 8.7
epss: "54%"
vendor: "contiki-ng"
kev: false
exploited: false
published: "2026-08-06 22:18:10"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-18T22:35:55+02:00"
---

# CVE-2026-5855

> 8.7 HIGH · 🧪 PoC

## Beschreibung

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-Vektor

```
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
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Patch verfügbar (OSV)

- f1673b5766d4d4d514cefb8a0350f43653574997 (Commit)

## Referenzen

- <https://github.com/contiki-ng/contiki-ng>
- <https://github.com/contiki-ng/contiki-ng/pull/3165>
- <https://github.com/contiki-ng/contiki-ng/commit/f1673b5766d4d4d514cefb8a0350f43653574997>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-5855) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_