How severe is CVE-2021-3321?

CVE-2021-3321 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over an adjacent network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability high.

Is CVE-2021-3321 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3321?

CVE-2021-3321 affects Zephyrproject Zephyr. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3321?

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-2021-3321 published?

CVE-2021-3321 was published on 2021-10-12 and last updated on 2026-06-17.

CVE-2021-3321

CVE-2021-3321 is a high-severity vulnerability in Zephyrproject Zephyr with a CVSS 3.x base score of 7.5. 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-191.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.8
EPSS exploit prediction: 1% (50th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-191
Affected product: Zephyrproject Zephyr
Published: 2021-10-12
Last modified: 2026-06-17

Description

Integer Underflow in Zephyr in IEEE 802154 Fragment Reassembly Header Removal. Zephyr versions >= >=2.4.0 contain Integer Overflow to Buffer Overflow (CWE-680). For more information, see https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-w44j-66g7-xw99

Frequently asked questions

What is CVE-2021-3321?: Integer Underflow in Zephyr in IEEE 802154 Fragment Reassembly Header Removal. Zephyr versions >= >=2.4.0 contain Integer Overflow to Buffer Overflow (CWE-680). For more information, see https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-w44j-66g7-xw99
How severe is CVE-2021-3321?: CVE-2021-3321 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over an adjacent network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability high.
Is CVE-2021-3321 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3321?: CVE-2021-3321 affects Zephyrproject Zephyr. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3321?: 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-2021-3321 published?: CVE-2021-3321 was published on 2021-10-12 and last updated on 2026-06-17.

References

http://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-w44j-66g7-xw99

Affected products (1)

cpe:2.3:o:zephyrproject:zephyr:*:*:*:*:*:*:*:*

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