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CVE-2023-6399

20
FAUCET Score

CVE-2023-6399 is a format string vulnerability affecting multiple Zyxel firewall and VPN series devices, including ATP, USG FLEX, and USG20(W)-VPN, across various firmware versions. An authenticated IPSec VPN user can exploit this by sending a crafted hostname to an affected device with the "Device Insight" feature enabled, leading to Denial of Service (DoS) conditions for the "deviceid" daemon. Rated 6.5 MEDIUM, this vulnerability has a low attack complexity and requires authentication, but can result in high availability impact. There is currently no evidence of active exploitation, nor are there public exploit modules available in Metasploit, Nuclei, or ExploitDB. Despite this, the vulnerability has garnered some community discussion and media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
>= 5.10, < 5.37CPE matchmatch criteria
cpe:2.3:o:zyxel:atp100_firmware:*:*:*:*:*:*:*:*
5.37CPE matchmatch criteria
cpe:2.3:o:zyxel:atp100_firmware:5.37:-:*:*:*:*:*:*
5.37CPE matchmatch criteria
cpe:2.3:o:zyxel:atp100_firmware:5.37:patch1:*:*:*:*:*:*
>= 5.10, < 5.37CPE matchmatch criteria
cpe:2.3:o:zyxel:atp100w_firmware:*:*:*:*:*:*:*:*
5.37CPE matchmatch criteria
cpe:2.3:o:zyxel:atp100w_firmware:5.37:-:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.7MEDIUM

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

Attack Vector
ADJACENT_NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
2.1
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.65%
Probability of exploitation in next 30 days
EPSS Percentile
47.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0065 is in the 58th percentile among its peer group of 21,977 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

The average CVE in this peer group has 0.0 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-aps-02-20-2024
Vendor Advisory