What is CVE-2021-21279?

CVE-2021-21279 is a high-severity vulnerability in Contiki-Ng, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 7.5/10. Published 2021-06-18.

How severe is CVE-2021-21279?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Contiki-Ng

CVE-2021-21279

Contiki-NG is an open-source, cross-platform operating system for internet of things devices. In verions prior to 4.6, an attacker can perform a denial-of-service attack by triggering an infinite loop in the processing of IPv6 neighbor solicitation (NS) messages. This type of attack can effectively shut down the operation of the system because of the cooperative scheduling used for the main parts of Contiki-NG and its communication stack. The problem has been patched in Contiki-NG 4.6. Users can apply the patch for this vulnerability out-of-band as a workaround.

Published 2021-06-18 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.010 (60.7th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 61st percentile — 60.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.010 · newest: 0.010 · change: 0.000

Affected products

Contiki-Ng — versions < 4.6

Weakness classification (CWE)

CWE-835 — Loop with Unreachable Exit Condition (Infinite Loop)

References

github.com/contiki-ng/contiki-ng/security/advisories/GHSA-rr5j-j8m8-fc4f (Third Party Advisory)

Frequently asked questions

What is CVE-2021-21279?: CVE-2021-21279 is a high-severity vulnerability in Contiki-Ng, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 7.5/10. Published 2021-06-18.
How severe is CVE-2021-21279?: High severity. CVSS v3 base score is 7.5 out of 10.