Home/CVE/A buffer overflow vulnerability in the Zyxel ATP series firmware versions 4.32 through 5.36 Patch 2, USG FLEX series fir
CVE

CVE-2023-34140

A buffer overflow vulnerability in the Zyxel ATP series firmware versions 4.32 through 5.36 Patch 2, USG FLEX series fir

A buffer overflow vulnerability in the Zyxel ATP series firmware versions 4.32 through 5.36 Patch 2, USG FLEX series firmware versions 4.50 through 5.36 Patch 2, USG FLEX 50(W) series firmware versions 4.16 through 5.36 Patch 2, USG20(W)-VPN series firmware versions 4.16 through 5.36 Patch 2, VPN series firmware versions 4.30 through 5.36 Patch 2, NXC2500 firmware versions 6.10(AAIG.0) through 6.10(AAIG.3), and NXC5500 firmware versions 6.10(AAOS.0) through 6.10(AAOS.4), could allow an unauthenticated, LAN-based attacker to cause denial of service (DoS) conditions by sending a crafted request to the CAPWAP daemon.

MEDIUM · CVSS 6.5 EPSS 0.00137
Monitor
  • No active-exploitation, high-EPSS, or public-exploit signals - routine patching cadence
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
▤

Affected Products & Versions

24
zyxel usg 20w-vpn firmware>= 4.16 and < 5.37
zyxel usg 2200-vpn firmware>= 4.30 and < 5.37
zyxel usg flex 100 firmware>= 4.50 and < 5.37
zyxel usg flex 100w firmware>= 4.50 and < 5.37
zyxel usg flex 200 firmware>= 4.50 and < 5.37
zyxel usg flex 50 firmware>= 4.50 and < 5.37
zyxel usg flex 500 firmware>= 4.50 and < 5.37
zyxel usg flex 50w firmware>= 4.50 and < 5.37
▣

Scoring & Timeline

6.5
MEDIUM · CVSS v3.1 · security@zyxel.com.tw
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD17 Jul 2023 · 06:15 PM
CVSS VectorCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
no
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
🔗

References & Sources

1
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-vulnerabilities-in-firewalls-and-wlan-controllersVendor Advisory
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