How severe is CVE-2021-3329?

CVE-2021-3329 has a CVSS 3.x base score of 9.6, rated critical severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity high, and availability high.

Is CVE-2021-3329 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (45th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3329?

CVE-2021-3329 primarily affects Zephyrproject Zephyr. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-3329?

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

When was CVE-2021-3329 published?

CVE-2021-3329 was published on 2023-02-26 and last updated on 2026-06-17.

CVE-2021-3329

CVE-2021-3329 is a critical-severity vulnerability in Zephyrproject Zephyr with a CVSS 3.x base score of 9.6. 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-665.

Key facts

Severity: Critical (CVSS 3.x base score 9.6)
EPSS exploit prediction: 1% (45th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-665
Affected product: Zephyrproject Zephyr
Published: 2023-02-26
Last modified: 2026-06-17

Description

Lack of proper validation in HCI Host stack initialization can cause a crash of the bluetooth stack

Frequently asked questions

What is CVE-2021-3329?: Lack of proper validation in HCI Host stack initialization can cause a crash of the bluetooth stack
How severe is CVE-2021-3329?: CVE-2021-3329 has a CVSS 3.x base score of 9.6, rated critical severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity high, and availability high.
Is CVE-2021-3329 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (45th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3329?: CVE-2021-3329 primarily affects Zephyrproject Zephyr. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-3329?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-3329 published?: CVE-2021-3329 was published on 2023-02-26 and last updated on 2026-06-17.

References

https://zephyrprojectsec.atlassian.net/browse/ZEPSEC-117

Affected products (4)

cpe:2.3:o:zephyrproject:zephyr:2.4.0:-:*:*:*:*:*:*
cpe:2.3:o:zephyrproject:zephyr:2.4.0:rc1:*:*:*:*:*:*
cpe:2.3:o:zephyrproject:zephyr:2.4.0:rc2:*:*:*:*:*:*
cpe:2.3:o:zephyrproject:zephyr:2.4.0:rc3:*:*:*:*:*:*

More vulnerabilities in Zephyrproject Zephyr

CVE-2022-3806 — Critical (CVSS 9.8): Inconsistent handling of error cases in bluetooth hci may lead to a double free condition of a network buffer.
CVE-2017-14199 — Critical (CVSS 9.8): A buffer overflow has been found in the Zephyr Project's getaddrinfo() implementation in 1.9.0 and 1.10.0.
CVE-2018-1000800 — Critical (CVSS 9.8): zephyr-rtos version 1.12.0 contains a NULL base pointer reference vulnerability in sys_ring_buf_put(),…
CVE-2023-0397 — Critical (CVSS 9.6): A malicious / defect bluetooth controller can cause a Denial of Service due to unchecked input in…
CVE-2021-3966 — Critical (CVSS 9.6): usb device bluetooth class includes a buffer overflow related to implementation of net_buf_add_mem.
CVE-2021-3625 — Critical (CVSS 9.6): Buffer overflow in Zephyr USB DFU DNLOAD. Zephyr versions >= v2.5.0 contain Heap-based Buffer Overflow (CWE-122). For…

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Other CWE-665 (Improper Initialization) vulnerabilities

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CVE-2021-41264 — Critical (CVSS 9.8): OpenZeppelin Contracts is a library for smart contract development. In affected versions upgradeable contracts using…
CVE-2019-10196 — Critical (CVSS 9.8): A flaw was found in http-proxy-agent, prior to version 2.1.0. It was discovered http-proxy-agent passes an auth option…
CVE-2015-8367 — Critical (CVSS 9.8): The phase_one_correct function in Libraw before 0.17.1 allows attackers to cause memory errors and possibly execute…
CVE-2019-14271 — Critical (CVSS 9.8): In Docker 19.03.x before 19.03.1 linked against the GNU C Library (aka glibc), code injection can occur when the…

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