How severe is CVE-2021-35028?

CVE-2021-35028 has a CVSS 3.x base score of 7.3, rated high severity. It is exploitable over an adjacent network with high attack complexity, requires high privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-35028 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-35028?

CVE-2021-35028 affects Zyxel Zywall Vpn2s Firmware. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-35028?

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-2021-35028 published?

CVE-2021-35028 was published on 2021-09-29 and last updated on 2026-06-17.

CVE-2021-35028

CVE-2021-35028 is a high-severity vulnerability in Zyxel Zywall Vpn2s Firmware with a CVSS 3.x base score of 7.3. 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-78.

Key facts

Severity: High (CVSS 3.x base score 7.3)
CVSS v2: 7.2
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-78
Affected product: Zyxel Zywall Vpn2s Firmware
Published: 2021-09-29
Last modified: 2026-06-17

Description

A command injection vulnerability in the CGI program of the Zyxel VPN2S firmware version 1.12 could allow an authenticated, local user to execute arbitrary OS commands.

Frequently asked questions

What is CVE-2021-35028?: A command injection vulnerability in the CGI program of the Zyxel VPN2S firmware version 1.12 could allow an authenticated, local user to execute arbitrary OS commands.
How severe is CVE-2021-35028?: CVE-2021-35028 has a CVSS 3.x base score of 7.3, rated high severity. It is exploitable over an adjacent network with high attack complexity, requires high privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-35028 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-35028?: CVE-2021-35028 affects Zyxel Zywall Vpn2s Firmware. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-35028?: 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-2021-35028 published?: CVE-2021-35028 was published on 2021-09-29 and last updated on 2026-06-17.

References

https://www.zyxel.com/support/Zyxel_security_advisory_for_directory_traversal_and_command_injection_vulnerabilities_of_VPN2S_Firewall.shtml

Affected products (1)

cpe:2.3:o:zyxel:zywall_vpn2s_firmware:1.12\(abln.0\)c0:*:*:*:*:*:*:*

More vulnerabilities in Zyxel Zywall Vpn2s Firmware

CVE-2023-34139 — High (CVSS 8.8): A command injection vulnerability in the Free Time WiFi hotspot feature of the Zyxel USG FLEX series firmware versions…
CVE-2023-33012 — High (CVSS 8.8): A command injection vulnerability in the configuration parser of the Zyxel ATP series firmware versions 5.10 through…
CVE-2023-33011 — High (CVSS 8.8): A format string vulnerability in the Zyxel ATP series firmware versions 5.10 through 5.36 Patch 2, USG FLEX series…
CVE-2023-28767 — High (CVSS 8.8): The configuration parser fails to sanitize user-controlled input in the Zyxel ATP series firmware versions 5.10 through…
CVE-2023-34141 — High (CVSS 8.0): A command injection vulnerability in the access point (AP) management feature of the Zyxel ATP series firmware versions…
CVE-2023-34138 — High (CVSS 8.0): A command injection vulnerability in the hotspot management feature of the Zyxel ATP series firmware versions 4.60…

All CVEs affecting Zyxel Zywall Vpn2s Firmware →

Other CWE-78 (OS Command Injection) vulnerabilities

CVE-2026-56004 — Critical (CVSS 10.0): A shellcode injection in the mercurial handler of the obs tar_scm source service before version 0.12.4 could be used by…
CVE-2026-56415 — Critical (CVSS 10.0): Storage Concentrator (SC & SCVM) contains a command injection vulnerability within the debug.pl script that is…
CVE-2026-56413 — Critical (CVSS 10.0): Storage Concentrator (SC & SCVM) contains a command injection vulnerability in the ms_service.pl service, which listens…
CVE-2026-49869 — Critical (CVSS 10.0): Kestra is an open-source, event-driven orchestration platform. Prior to 1.0.45 and 1.3.21, AuthenticationFilter in…
CVE-2026-49261 — Critical (CVSS 10.0): MariaDB server is a community developed fork of MySQL server. Versions 10.6.1 through 10.6.26, 10.11.1 through…
CVE-2026-10520 — Critical (CVSS 10.0): An OS Command Injection vulnerability in Ivanti Sentry before the R10.5.2, R10.6.2 and R10.7.1 versions allows a…

Browse all CWE-78 (OS Command Injection) vulnerabilities →