How severe is CVE-2023-35138?

CVE-2023-35138 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2023-35138 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 40% (98th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-35138?

CVE-2023-35138 primarily affects Zyxel Nas326 Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2023-35138?

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-2023-35138 published?

CVE-2023-35138 was published on 2023-11-30 and last updated on 2026-06-17.

CVE-2023-35138

CVE-2023-35138 is a critical-severity vulnerability in Zyxel Nas326 Firmware with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 40% places it in the 98th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-78.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
EPSS exploit prediction: 40% (98th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-78
Affected product: Zyxel Nas326 Firmware
Published: 2023-11-30
Last modified: 2026-06-17

Description

A command injection vulnerability in the “show_zysync_server_contents” function of the Zyxel NAS326 firmware version V5.21(AAZF.14)C0 and NAS542 firmware version V5.21(ABAG.11)C0 could allow an unauthenticated attacker to execute some operating system (OS) commands by sending a crafted HTTP POST request.

Frequently asked questions

What is CVE-2023-35138?: A command injection vulnerability in the “show_zysync_server_contents” function of the Zyxel NAS326 firmware version V5.21(AAZF.14)C0 and NAS542 firmware version V5.21(ABAG.11)C0 could allow an unauthenticated attacker to execute some operating system (OS) commands by sending a crafted HTTP POST request.
How severe is CVE-2023-35138?: CVE-2023-35138 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2023-35138 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 40% (98th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-35138?: CVE-2023-35138 primarily affects Zyxel Nas326 Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2023-35138?: 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-2023-35138 published?: CVE-2023-35138 was published on 2023-11-30 and last updated on 2026-06-17.

References

https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-authentication-bypass-and-command-injection-vulnerabilities-in-nas-products

Affected products (2)

cpe:2.3:o:zyxel:nas326_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:nas542_firmware:*:*:*:*:*:*:*:*

More vulnerabilities in Zyxel Nas326 Firmware

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