How severe is CVE-2021-21280?

CVE-2021-21280 has a CVSS 3.x base score of 8.6, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability high.

Is CVE-2021-21280 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (61st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21280?

CVE-2021-21280 affects Contiki-ng. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-21280?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-21280 published?

CVE-2021-21280 was published on 2021-06-18 and last updated on 2026-06-17.

CVE-2021-21280

CVE-2021-21280 is a high-severity vulnerability in Contiki-ng with a CVSS 3.x base score of 8.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.

Key facts

Severity: High (CVSS 3.x base score 8.6)
CVSS v2: 7.5
EPSS exploit prediction: 1% (61st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Contiki-ng
Published: 2021-06-18
Last modified: 2026-06-17

Description

Contiki-NG is an open-source, cross-platform operating system for internet of things devices. It is possible to cause an out-of-bounds write in versions of Contiki-NG prior to 4.6 when transmitting a 6LoWPAN packet with a chain of extension headers. Unfortunately, the written header is not checked to be within the available space, thereby making it possible to write outside the buffer. The problem has been patched in Contiki-NG 4.6. Users can apply the patch for this vulnerability out-of-band as a workaround.

Frequently asked questions

What is CVE-2021-21280?: Contiki-NG is an open-source, cross-platform operating system for internet of things devices. It is possible to cause an out-of-bounds write in versions of Contiki-NG prior to 4.6 when transmitting a 6LoWPAN packet with a chain of extension headers. Unfortunately, the written header is not checked to be within the available space, thereby making it possible to write outside the buffer. The problem has been patched in Contiki-NG 4.6. Users can apply the patch for this vulnerability out-of-band as a workaround.
How severe is CVE-2021-21280?: CVE-2021-21280 has a CVSS 3.x base score of 8.6, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability high.
Is CVE-2021-21280 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (61st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21280?: CVE-2021-21280 affects Contiki-ng. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-21280?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-21280 published?: CVE-2021-21280 was published on 2021-06-18 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:o:contiki-ng:contiki-ng:*:*:*:*:*:*:*:*

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