CVE-2021-21279: Infinite loop in IPv6 neighbor solicitation processing

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-06-18 · updated 2026-06-17
Weakness: CWE-835

Description

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.

Affected products

contiki-ng: before 4.6 — fixed in 4.6

How to fix

Upgrade to a fixed version: contiki-ng 4.6. Check the vendor advisory for mitigations.

References

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