Vulnerability Intelligence Report
Zyxel Multiple Firewalls Buffer Overflow Vulnerability
CVE-2023-33010
A buffer overflow vulnerability in the ID processing function in Zyxel ATP series firmware versions 4.32 through 5.36 Patch 1, USG FLEX series firmware versions 4.50 through 5.36 Patch 1, USG FLEX 50(W) firmware versions 4.25 through 5.36 Patch 1, USG20(W)-VPN firmware versions 4.25 through 5.36 Patch 1, VPN series firmware versions 4.30 through 5.36 Patch 1, ZyWALL/USG series firmware versions 4.25 through 4.73 Patch 1, could allow an unauthenticated attacker to cause denial-of-service (DoS) conditions and even a remote code execution on an affected device.
CISA KEV
SSVC: Active Exploitation
Automatable
CVSS Base Score
9.8
CRITICAL
Exploitability:3.9
Impact Score:5.9
EPSS Probability:28.81%
Executive Threat Verdict
Evaluating...
Evaluating Threat Landscape...
Assessing known weaponization, exploitation telemetry, and federal advisories.
Attack Surface
—
Authentication
—
Weaponization
—
SSVC Action
—
Weaknesses (CWE)
CWE-120 ↗CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Affected Products & Versions
| Vendor | Product | Affected Versions |
|---|---|---|
| Zyxel | ATP series firmware | 4.32 through 5.36 Patch 1 (affected) |
| Zyxel | USG FLEX series firmware | 4.50 through 5.36 Patch 1 (affected) |
| Zyxel | USG FLEX 50(W) firmware | 4.25 through 5.36 Patch 1 (affected) |
| Zyxel | USG20(W)-VPN firmware | 4.25 through 5.36 Patch 1 (affected) |
| Zyxel | VPN series firmware | 4.30 through 5.36 Patch 1 (affected) |
| Zyxel | ZyWALL/USG series firmware | 4.25 through 4.73 Patch 1 (affected) |
References & Technical Advisories
No reference links found.
Threat Intelligence Signals
Identity & Timeline
| Status | PUBLISHED |
| Assigning Authority | Zyxel Corporation · Vendor · Taiwan |
| Reserved | 2023-05-17T00:00:00 |
| Published | 2023-05-24T00:00:00 |
| Last Updated | 2025-10-21T23:05:47 |
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