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CVE-2023-27992

94
FAUCET Score

CVE-2023-27992 is a critical pre-authentication command injection vulnerability affecting Zyxel NAS326, NAS540, and NAS542 devices running specific older firmware versions. This flaw allows an unauthenticated attacker to remotely execute operating system commands by sending a crafted HTTP request. With a CVSS score of 9.8 (Critical), it presents a severe risk due to its network-based attack vector, low attack complexity, and complete compromise of confidentiality, integrity, and availability. This vulnerability is actively exploited in the wild, as confirmed by its inclusion in CISA's KEV catalog, and has garnered significant community discussion and media coverage, despite no public exploit code being readily available on platforms like Metasploit or ExploitDB.

Impacted Technologies

VendorProductVersion(s)CPE
< 5.21\(aazf.14\)c0CPE matchmatch criteria
cpe:2.3:o:zyxel:nas326_firmware:*:*:*:*:*:*:*:*
< 5.21\(aatb.11\)c0CPE matchmatch criteria
cpe:2.3:o:zyxel:nas540_firmware:*:*:*:*:*:*:*:*
< 5.21\(abag.11\)c0CPE matchmatch criteria
cpe:2.3:o:zyxel:nas542_firmware:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
84.19%
Probability of exploitation in next 30 days
EPSS Percentile
99.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Added to KEV · Jun 23, 2023
This CVE's current EPSS score of 0.8419 is in the 98th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

cisa.gov / known-exploited-vulnerabilities-catalog
US Government Resource
zyxel.com / global/en/support/security-advisories/zyxel-security-advisory-for-pre-authentication-command-injection-vulnerability-in-nas-products
PatchVendor Advisory