CVE-2023-33009: Zyxel Multiple Firewalls Buffer Overflow Vulnerability

CVE-2023-33009 · Severity: critical · CVSS 9.8 · Exploited in the wild · Published 2023-06-05

A buffer overflow vulnerability exists in the notification function of multiple Zyxel firewall series. An unauthenticated remote attacker can exploit this to cause a denial-of-service (DoS) condition or execute arbitrary code on the affected device.

Technologies: Zyxel Firewalls, Zyxel Multiple Firewalls. Vendors: Zyxel.

Quick answers

Is CVE-2023-33009 exploited in the wild?
Yes. CVE-2023-33009 is known to be exploited in the wild, first recorded on 5 June 2023. Treat it as urgent.
How severe is CVE-2023-33009?
Critical severity, with a CVSS score of 9.8, published 5 June 2023.
Which products and versions are affected?
Zyxel ATP series firmware 4.60 through 5.36 Patch 1; Zyxel USG FLEX series firmware 4.60 through 5.36 Patch 1; Zyxel USG FLEX 50(W) firmware 4.60 through 5.36 Patch 1; Zyxel USG20(W)-VPN firmware 4.60 through 5.36 Patch 1; and 2 more.
Is there a fix for CVE-2023-33009?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2023-33009 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2023-33009?
Check whether you run Zyxel Firewalls or Zyxel Multiple Firewalls. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Affected products

  • Zyxel ATP series firmware 4.60 through 5.36 Patch 1
  • Zyxel USG FLEX series firmware 4.60 through 5.36 Patch 1
  • Zyxel USG FLEX 50(W) firmware 4.60 through 5.36 Patch 1
  • Zyxel USG20(W)-VPN firmware 4.60 through 5.36 Patch 1
  • Zyxel VPN series firmware 4.60 through 5.36 Patch 1
  • Zyxel ZyWALL/USG series firmware 4.60 through 4.73 Patch 1

Timeline

  • 2023-05-24: disclosed: Date based on CVE ID assignment/early reporting context
  • 2023-06-05: advisory
  • 2023-06-05: kev added: Added to CISA Known Exploited Vulnerabilities Catalog
  • 2023-06-05: exploited: Confirmed as exploited in the wild per CISA KEV catalog and advisory.

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