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CVE-2023-34140

20
FAUCET Score

CVE-2023-34140 is a buffer overflow vulnerability affecting multiple Zyxel network devices, including various ATP, USG FLEX, USG20(W)-VPN, VPN, NXC2500, and NXC5500 series firmware versions. An unauthenticated attacker on the local area network (LAN) can exploit this flaw by sending a specially crafted request to the CAPWAP daemon, leading to a denial-of-service (DoS) condition. Rated with a CVSS score of 6.5 (Medium), this vulnerability has a low attack complexity and requires no user interaction, but its impact is limited to availability. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
>= 4.16, < 5.37CPE matchmatch criteria
cpe:2.3:o:zyxel:usg_20w-vpn_firmware:*:*:*:*:*:*:*:*
>= 4.30, < 5.37CPE matchmatch criteria
cpe:2.3:o:zyxel:usg_2200-vpn_firmware:*:*:*:*:*:*:*:*
>= 4.50, < 5.37CPE matchmatch criteria
cpe:2.3:o:zyxel:usg_flex_100_firmware:*:*:*:*:*:*:*:*
>= 4.50, < 5.37CPE matchmatch criteria
cpe:2.3:o:zyxel:usg_flex_100w_firmware:*:*:*:*:*:*:*:*
>= 4.50, < 5.37CPE matchmatch criteria
cpe:2.3:o:zyxel:usg_flex_200_firmware:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
ADJACENT_NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.30%
Probability of exploitation in next 30 days
EPSS Percentile
22.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0030 is in the 33rd percentile among its peer group of 1,802 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

zyxel.com / global/en/support/security-advisories/zyxel-security-advisory-for-multiple-vulnerabilities-in-firewalls-and-wlan-controllers
Vendor Advisory