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CVE-2026-5855

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.

Published Aug 6, 2026CWE-125EPSS 0.72%

Overview

CVE-2026-5855 is a high-severity vulnerability. It was published on August 6, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/contiki-ng/contiki-ngGitHubgithub.com/contiki-ng/contiki-ng/commit/f1673b5766d4d4d514cefb8a0350f43653574997GitHubgithub.com/contiki-ng/contiki-ng/pull/3165

How CyberStrike helps

Frequently asked questions

What is CVE-2026-5855?

CVE-2026-5855 is a high-severity vulnerability. It was published on August 6, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-5855?

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-5855?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-5855?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-5855 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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