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VulnerabilityPublished Updated

CVE-2023-4473: Zyxel NAS326 firmware · OS Command Injection

Affects Zyxel NAS326 firmwareSource CVE Database V5

0

Not known to be exploited · 41% EPSS · CVSS 9.8 Critical.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
41.3% chance of exploitation in 30 days – higher than 98% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 30 Nov 2023

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

AI-suggested

  1. Immediately restrict network access to Zyxel NAS management interfaces by implementing firewall rules to allow only trusted IP addresses or internal networks.
  2. Disable remote management features if not strictly necessary, especially on WAN interfaces.
  3. Monitor network traffic for suspicious HTTP requests targeting the NAS web server, particularly unusual URL patterns that could indicate command injection attempts.
  4. Employ network segmentation to isolate NAS devices from critical infrastructure and limit lateral movement opportunities.
  5. Regularly back up NAS data to offline or immutable storage to mitigate ransomware risks.
  6. Stay alert for official firmware updates from Zyxel addressing CVE-2023-4473 and apply patches immediately upon release.
  7. Consider deploying Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) with signatures or heuristics to detect and block command injection attempts targeting Zyxel NAS devices.
  8. Conduct internal audits to identify all Zyxel NAS devices in the environment and verify firmware versions to prioritize remediation efforts.
  9. Educate IT staff about this vulnerability and ensure incident response plans include scenarios involving NAS compromise.

Description

CVE-2023-4473 is a critical OS command injection vulnerability in Zyxel NAS326 and NAS542 firmware versions V5.21(AAZF.14)C0 and V5.21(ABAG.11)C0. It allows unauthenticated attackers to execute arbitrary OS commands by sending crafted URLs to the device's web server. The vulnerability stems from improper neutralization of special elements in OS commands (CWE-78). With a CVSS score of 9.8, it poses a severe risk to confidentiality, integrity, and availability without requiring authentication or user interaction. No public exploits are known yet, but the impact could be devastating if exploited.

References

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