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VulnerabilityPublished Updated

CVE-2023-4474: Zyxel NAS326 firmware · OS Command Injection

Affects Zyxel NAS326 firmwareSource CVE Database V5

0

Not known to be exploited · 29% EPSS · CVSS 9.8 Critical.

Data as of 26 Oct 2026, 10:12 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
29.7% 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 identify and inventory all Zyxel NAS326 and NAS542 devices running the affected firmware versions (V5.21(AAZF.14)C0 and V5.21(ABAG.11)C0).
  2. Monitor Zyxel’s official channels for firmware updates or patches addressing CVE-2023-4474 and apply them promptly once available.
  3. Until patches are released, restrict network access to vulnerable NAS devices by implementing strict firewall rules limiting inbound connections to trusted management networks only.
  4. Disable remote management interfaces exposed to the internet or untrusted networks to reduce exposure.
  5. Deploy network intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics to detect suspicious URL requests targeting the WSGI server.
  6. Conduct regular log analysis on NAS devices to identify anomalous or unauthorized command execution attempts.
  7. Segment NAS devices into isolated network zones to limit potential lateral movement if compromised.
  8. Educate IT and security teams about the vulnerability and encourage vigilance for unusual device behavior.
  9. Consider temporary replacement or removal of vulnerable devices in critical environments if patching is delayed.
  10. Implement strong backup and recovery procedures to mitigate impact of potential data loss or ransomware attacks.

Description

CVE-2023-4474 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 arises from improper neutralization of special elements in the WSGI server, allowing unauthenticated attackers to execute arbitrary OS commands via crafted URLs. The vulnerability has a CVSS score of 9.8, indicating high impact on confidentiality, integrity, and availability without requiring authentication or user interaction. Exploitation could lead to full system compromise, data theft, or service disruption. No public exploits are currently known, but the severity demands immediate attention.

References

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