Yes. CISA added Zyxel NAS vulnerability CVE-2023-27992 to its Known Exploited Vulnerabilities catalog in June 2023, indicating that it had been exploited in the wild. The flaw affects Zyxel NAS326, NAS540 and NAS542 devices running firmware 5.21 or earlier, and allows remote command execution without authentication. Owners should check Zyxel’s current advisory, install the applicable fix, and keep NAS management services off the open internet.
What is CVE-2023-27992?
CVE-2023-27992 is a pre-authentication command-injection vulnerability in certain Zyxel network-attached storage (NAS) devices. Zyxel’s advisory, reproduced by SecurityWeek, says an unauthenticated attacker could send a specially crafted HTTP request and execute operating-system commands remotely. In practical terms, an exposed, vulnerable device could be targeted without the attacker first signing in.
The vulnerability has a CVSS score of 9.8, as recorded by Zyxel and the CVE record in 2023. That score reflects technical severity; it is not a measure of how many devices were attacked or compromised.
Which Zyxel NAS models are affected?
The 2023 warning identified these models when running firmware version 5.21 or earlier:
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- Zyxel NAS326
- Zyxel NAS540
- Zyxel NAS542
Check the exact model and installed firmware against Zyxel’s security advisory index before deciding what firmware to install. The affected-version information above reflects the 2023 warning; the vendor’s current advisory is the place to confirm model-specific fixes and support status.
Has the vulnerability been exploited?
Yes. CISA warned on June 23, 2023 that CVE-2023-27992 was being exploited and added it to its Known Exploited Vulnerabilities catalog. SecurityWeek reported the warning on June 26, 2023. CISA required U.S. federal civilian agencies to remediate by July 14, 2023; that deadline applied to those agencies, not to all NAS owners.
Rank #2
- Value NAS with RAID for centralized storage and backup for all your devices. Check out the LS 700 for enhanced features, cloud capabilities, macOS 26, and up to 7x faster performance than the LS 200.
- Connect the LinkStation to your router and enjoy shared network storage for your devices. The NAS is compatible with Windows and macOS*, and Buffalo's US-based support is on-hand 24/7 for installation walkthroughs. *Only for macOS 15 (Sequoia) and earlier. For macOS 26, check out our LS 700 series.
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- Storage Purpose-Built for Data Security – A NAS designed to keep your data safe, the LS200 features a closed system to reduce vulnerabilities from 3rd party apps and SSL encryption for secure file transfers.
- Back Up Multiple Computers & Devices – NAS Navigator management utility and PC backup software included. NAS Navigator 2 for macOS 15 and earlier. You can set up automated backups of data on your computers.
Public reporting identified the in-the-wild exploitation status, but did not establish a named attacker, malware family, victim count or detailed attack chain. CISA’s listing is a reason to prioritize remediation, not evidence that a particular device has been compromised.
How to secure an affected Zyxel NAS
- Inventory your devices. Find every NAS326, NAS540 and NAS542 you manage, and record each device’s firmware version.
- Limit access while you check. Remove direct internet exposure to NAS management services. Restrict administration to a trusted local network or a VPN, and review logs for suspicious requests.
- Verify and install the vendor fix. Compare the model and firmware with Zyxel’s current security advisories, then follow the model-specific instructions to install the applicable patch.
- Isolate unsupported or unpatchable hardware. If Zyxel does not provide a fix for your device, keep it off untrusted networks and plan a replacement.
- Assess possible compromise separately. Patching or replacing hardware does not establish whether an exposed device was previously compromised. Preserve and review relevant logs, and investigate suspicious activity before treating the system as clean.
Should you replace an older Zyxel NAS?
Replacement is worth considering if your NAS cannot receive the applicable fix or is no longer supported. Compare the choices using these practical factors:
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| Factor | Patch and keep the device | Replace the device |
|---|---|---|
| Patch availability | Appropriate only if Zyxel provides a fix for the exact model and firmware; confirm in the vendor advisory. | May be necessary if the current device cannot be patched; confirm the replacement’s support and firmware status. |
| Vendor support lifecycle | Depends on the existing model’s current support status, which should be checked with Zyxel. | Check how long the prospective device is expected to receive security updates; a newer device is not automatically secure. |
| Internet exposure | Keep management access restricted to a trusted network or VPN. | Configure the same access restrictions on the replacement; replacement alone does not make internet-facing management safe. |
| Migration effort | Usually avoids moving data and services to different hardware. | Requires planning data, shares, accounts and services migration. |
| Backup compatibility | Check that existing backup jobs and recovery procedures still work after updating. | Confirm that data and backup formats can be migrated or restored on the new system. |
| Total cost | Includes the effort of patching, securing and maintaining the current NAS. | Includes replacement hardware and migration effort; current pricing and inventory are not established here. |
Whichever option you choose, do not assume that buying another NAS removes risk from an already exposed device. Secure access, supported firmware and a careful migration or incident review all matter.
Quick Recap
Best Value
- Value NAS with RAID for centralized storage and backup for all your devices. Check out the LS 700 for enhanced features, cloud capabilities, macOS 26, and up to 7x faster performance than the LS 200.
- Connect the LinkStation to your router and enjoy shared network storage for your devices. The NAS is compatible with Windows and macOS*, and Buffalo's US-based support is on-hand 24/7 for installation walkthroughs. *Only for macOS 15 (Sequoia) and earlier. For macOS 26, check out our LS 700 series.
- Subscription-Free Personal Cloud – Store, back up, and manage all your videos, music, and photos and access them anytime without paying any monthly fees.
- Storage Purpose-Built for Data Security – A NAS designed to keep your data safe, the LS200 features a closed system to reduce vulnerabilities from 3rd party apps and SSL encryption for secure file transfers.
- Back Up Multiple Computers & Devices – NAS Navigator management utility and PC backup software included. NAS Navigator 2 for macOS 15 and earlier. You can set up automated backups of data on your computers.
Rank #4
- Value NAS with RAID for centralized storage and backup for all your devices. Check out the LS 700 for enhanced features, cloud capabilities, macOS 26, and up to 7x faster performance than the LS 200.
- Connect the LinkStation to your router and enjoy shared network storage for your devices. The NAS is compatible with Windows and macOS*, and Buffalo's US-based support is on-hand 24/7 for installation walkthroughs. *Only for macOS 15 (Sequoia) and earlier. For macOS 26, check out our LS 700 series.
- Subscription-Free Personal Cloud – Store, back up, and manage all your videos, music, and photos and access them anytime without paying any monthly fees.
- Storage Purpose-Built for Data Security – A NAS designed to keep your data safe, the LS200 features a closed system to reduce vulnerabilities from 3rd party apps and SSL encryption for secure file transfers.
- Back Up Multiple Computers & Devices – NAS Navigator management utility and PC backup software included. NAS Navigator 2 for macOS 15 and earlier. You can set up automated backups of data on your computers.
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