CVE-2023-27992
CVE-2023-27992 is a security flaw in Zyxel Multiple Network-Attached Storage (NAS) Devices, firewalls and routers for homes and small businesses. Attackers can run commands on Zyxel Multiple Network-Attached Storage (NAS) Devices from anywhere, without logging in. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 23 Jun 2023.[1]
Zyxel Multiple Network-Attached Storage (NAS) Devices is in things households have: home and small-office routers, so the fix matters at home as much as at work. Zyxel has published a fix or advice.
Description
CISA calls it a multiple NAS devices command injection in Zyxel Multiple Network-Attached Storage (NAS) Devices. In its words: “Multiple Zyxel network-attached storage (NAS) devices contain a pre-authentication command injection vulnerability that could allow an unauthenticated attacker to execute commands remotely via a crafted HTTP request.”[1]
The CVE record adds: “The pre-authentication command injection vulnerability in the Zyxel NAS326 firmware versions prior to V5.21(AAZF.14)C0, NAS540 firmware versions prior to V5.21(AATB.11)C0, and NAS542 firmware versions prior to V5.21(ABAG.11)C0 could allow an unauthenticated attacker to execute some operating system (OS) commands remotely by sending a crafted HTTP request.”[2]
The underlying weakness is OS command injection (CWE-78), in MITRE’s list of common software weaknesses.
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by the organisation that published the CVE using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Zyxel’s advisory has them[3]. CISA names the product as Zyxel Multiple Network-Attached Storage (NAS) Devices.
Every device with Zyxel Multiple Network-Attached Storage (NAS) Devices needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 23 Jun 2023, 4 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 14 Jul 2023 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 82%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Zyxel has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Update Zyxel Multiple Network-Attached Storage (NAS) Devices now.Open the router’s app, or its admin page in a browser, and look for a firmware update. Then turn on automatic updates, so the next fix arrives on its own.
- If the maker has stopped updating it, replace it.Routers stop getting fixes after a few years, and attackers keep a list of the ones that did. If there’s no newer firmware, it won’t be fixed.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 9.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 82%.[4] |
See also
Other Zyxel Multiple Network-Attached Storage (NAS) Devices flaws
- CVE-2020-9054: multiple NAS devices OS command injection ·
Other Zyxel flaws
- CVE-2026-7273, Zyxel GS1900 Series Switches: stack-based buffer overflow ·
- CVE-2024-40891, Zyxel DSL CPE Devices: DSL CPE OS command injection ·
- CVE-2024-40890, Zyxel DSL CPE Devices: DSL CPE OS command injection ·
- CVE-2024-11667, Zyxel Multiple Firewalls: path traversal ·
- CVE-2017-6884, Zyxel EMG2926 Routers: command injection ·
Other OS command injection flaws
- CVE-2026-110447, Collabora Online – Built-in CODE Server: online – built-in CODE server OS command injection ·
- CVE-2026-106931, EG Secure Solutions SiteGuard Server Edition: OS command injection ·
- CVE-2026-83549, SonicWall SMA1000 Appliances: OS command injection ·
- CVE-2026-49869, Kestra OSS: OSS OS command injection ·
- CVE-2026-73570, Synacor Zimbra Collaboration Suite (ZCS): OS command injection ·
Added the same day
- CVE-2023-32439, Apple devices: webKit type confusion ·
- CVE-2023-32435, Apple devices: webKit memory corruption ·
- CVE-2023-32434, Apple devices: integer overflow ·
- CVE-2023-20867, VMware Tools: authentication bypass ·
Every Zyxel flaw on CISA’s list · Everything added in June 2023
References
- ^ Cybersecurity and Infrastructure Security Agency. “Zyxel Multiple NAS Devices Command Injection Vulnerability”. Known Exploited Vulnerabilities Catalog, added 23 Jun 2023.
- ^ National Institute of Standards and Technology. “CVE-2023-27992 Detail”. National Vulnerability Database, published 19 Jun 2023.
- ^ Zyxel. Advisories and fixes: zyxel.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.823, percentile 99.7, 31 Oct 2026.
- CVE Program. “CVE-2023-27992”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.