HOMEVULNERABILITIESCVE-2023-35138
CRITICAL

CVE-2023-35138

CWE-78Published: November 30, 2023· Updated: Jun 17, 2026

9.8
CVSS v3.1

Official Description

A command injection vulnerability in the “show_zysync_server_contents” function of the Zyxel NAS326 firmware version V5.21(AAZF.14)C0 and NAS542 firmware version V5.21(ABAG.11)C0 could allow an unauthenticated attacker to execute some operating system (OS) commands by sending a crafted HTTP POST request.

NVD Source

Risk Analysis

Zyxel NAS devices are vulnerable to command injection, allowing unauthenticated attackers to execute OS commands via malicious HTTP POST requests. This critical flaw is rated 9.8 on the CVSS scale.

No public exploit is known, and the vulnerability is not in the CISA KEV. It is remotely exploitable with low attack complexity.

Recommended Action

Apply the latest firmware updates provided by Zyxel for the NAS326 and NAS542 models.

Generated by the CTIWATCH analysis pipeline from this CVE's metadata (CVSS, EPSS, KEV status, exploit intelligence). Verify against vendor advisories before acting.

Technical Analysis

CVE-2023-35138 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

zyxel4 product(s)
nas326 firmwarenas326nas542 firmwarenas542
Source: NVD CPE · 4 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-authentication-bypass-and-command-injection-vulnerabilities-in-nas-products
PATCHhttps://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-authentication-bypass-and-command-injection-vulnerabilities-in-nas-products

All References (2)

→
https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-authentication-bypass-and-command-injection-vulnerabilities-in-nas-productsPatch · Vendor Advisory
→
https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-authentication-bypass-and-command-injection-vulnerabilities-in-nas-productsPatch · Vendor Advisory

Quick Facts

CVE IDCVE-2023-35138
CVSS Score9.8 / 10
SeverityCRITICAL
WeaknessCWE-78
CISA KEVNo
Affected1 vendor(s)
PublishedNov 30, 2023

Related CVEs (CWE-78)

CVE-2011-0372
10.0
CVE-2010-3757
10.0
CVE-2011-0271
10.0
CVE-2010-2445
10.0
CVE-2010-3754
10.0
CVE-2011-0381
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2023-35138 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
← All Vulnerabilities·Search for CVE-2023-35138·NVD