CVE-2026-5855
Out-of-bounds read in Contiki-NG LwM2M TLV parser leaks heap memory.
Is CVE-2026-5855 being exploited?
Not confirmed. CVE-2026-5855 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.54% probability of exploitation in the next 30 days.
How severe is CVE-2026-5855?
CVE-2026-5855 is rated High. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-5855?
Not known from our data. No patch reference has been recorded for CVE-2026-5855, which is not the same as no patch existing — a fix may have shipped without a tagged reference, or after this record was written. The vendor advisory is the only authority on whether a fix exists, and mitigations may be available regardless.
What does CVE-2026-5855 affect?
CVE-2026-5855 affects Contiki-NG (os/services/lwm2m/lwm2m-tlv.c), LwM2M endpoints on constrained IoT devices, Devices using LwM2M NoSec. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-5855?
Apply vendor patch when available; disable NoSec; restrict/block CoAP WRITE from untrusted networks.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Crafted CoAP WRITE causes OOB heap reads, leaking memory (keys, peer addresses) and corrupting parse state; unauthenticated in NoSec mode.
Immediate action required
- affected< f1673b5766d4d4d514cefb8a0350f43653574997
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.