How severe is CVE-2021-35033?

CVE-2021-35033 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-35033 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (32nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-35033?

CVE-2021-35033 primarily affects Zyxel Nbg6818 Firmware. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-35033?

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-2021-35033 published?

CVE-2021-35033 was published on 2021-11-23 and last updated on 2026-06-17.

CVE-2021-35033

CVE-2021-35033 is a high-severity vulnerability in Zyxel Nbg6818 Firmware with a CVSS 3.x base score of 7.8. 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-287.

Key facts

Severity: High (CVSS 3.x base score 7.8)
CVSS v2: 6.9
EPSS exploit prediction: 0% (32nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-287
Affected product: Zyxel Nbg6818 Firmware
Published: 2021-11-23
Last modified: 2026-06-17

Description

A vulnerability in specific versions of Zyxel NBG6818, NBG7815, WSQ20, WSQ50, WSQ60, and WSR30 firmware with pre-configured password management could allow an attacker to obtain root access of the device, if the local attacker dismantles the device and uses a USB-to-UART cable to connect the device, or if the remote assistance feature had been enabled by an authenticated user.

Frequently asked questions

What is CVE-2021-35033?: A vulnerability in specific versions of Zyxel NBG6818, NBG7815, WSQ20, WSQ50, WSQ60, and WSR30 firmware with pre-configured password management could allow an attacker to obtain root access of the device, if the local attacker dismantles the device and uses a USB-to-UART cable to connect the device, or if the remote assistance feature had been enabled by an authenticated user.
How severe is CVE-2021-35033?: CVE-2021-35033 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-35033 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (32nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-35033?: CVE-2021-35033 primarily affects Zyxel Nbg6818 Firmware. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-35033?: 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-2021-35033 published?: CVE-2021-35033 was published on 2021-11-23 and last updated on 2026-06-17.

References

Affected products (6)

cpe:2.3:o:zyxel:nbg6818_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:nbg7815_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:wsq20_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:wsq50_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:wsq60_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:wsr30_firmware:*:*:*:*:*:*:*:*

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