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CVE-2020-9054
KEV PoC moderatePre-Authentication OS Command Injection in Zyxel NAS Devices
CISA: Zyxel Multiple NAS Devices OS Command Injection Vulnerability
CVSS 3.1
9.8 critical
EPSS
100%p100
Published
()
KEV added
AI analysis
CVE-2020-9054 is a pre-authentication OS command injection flaw (CWE-78) in multiple Zyxel network-attached storage (NAS) devices. A remote, unauthenticated attacker can send crafted input to the devices' web interface to inject and execute arbitrary OS commands without logging in, resulting in remote code execution on the NAS. Successful exploitation gives the attacker control of the device, which can be used to access, alter or destroy stored data and to pivot into the network the NAS is attached to. Organizations and users running affected Zyxel NAS models are at risk, especially where the management web interface is reachable from the internet. The flaw was added to CISA's Known Exploited Vulnerabilities catalog on 2022-03-25, confirming exploitation in the wild; EPSS assigns a 100% probability of exploitation within 30 days, while no public proof-of-concept is known and any ransomware use is unconfirmed.
What to do: Apply the firmware updates specified in Zyxel's advisory, per CISA's required action, prioritizing any NAS whose web interface is exposed to the internet. Until patched, restrict the NAS management interface to trusted networks or VPN access and do not expose the admin UI directly to the internet. Because exploitation is confirmed in the wild, check affected devices for indicators of compromise, such as unexpected accounts, scheduled jobs, or outbound connections.
Affected
| Zyxel | — |
Estimated exposure
moderateplausibly tens of thousands of affected devices installed worldwide, with only a low-thousands subset directly internet-exposed — Based on Zyxel's minor share of the consumer/SOHO NAS market (well behind the leading vendors) and the typical deployment of these NAS units behind NAT rather than directly internet-facing, the installed base is plausibly in the tens of…
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description
Multiple ZyXEL network-attached storage (NAS) devices running firmware version 5.21 contain a pre-authentication command injection vulnerability, which may allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable device. ZyXEL NAS devices achieve authentication by using the weblogin.cgi CGI executable. This program fails to properly sanitize the username parameter that is passed to it. If the username parameter contains certain characters, it can allow command injection with the privileges of the web server that runs on the ZyXEL device. Although the web server does not run as the root user, ZyXEL devices include a setuid utility that can be leveraged to run any command with root privileges. As such, it should be assumed that exploitation of this vulnerability can lead to remote code execution with root privileges. By sending a specially-crafted HTTP POST or GET request to a vulnerable ZyXEL device, a remote, unauthenticated attacker may be able to execute arbitrary code on the device. This may happen by directly connecting to a device if it is directly exposed to an attacker. However, there are ways to trigger such crafted requests even if an attacker does not have direct connectivity to a vulnerable devices. For example, simply visiting a website can result in the compromise of any ZyXEL device that is reachable from the client system. Affected products include: NAS326 before firmware V5.21(AAZF.7)C0 NAS520 before firmware V5.21(AASZ.3)C0 NAS540 before firmware V5.21(AATB.4)C0 NAS542 before firmware V5.21(ABAG.4)C0 ZyXEL has made firmware updates available for NAS326, NAS520, NAS540, and NAS542 devices. Affected models that are end-of-support: NSA210, NSA220, NSA220+, NSA221, NSA310, NSA310S, NSA320, NSA320S, NSA325 and NSA325v2
CISA Known Exploited Vulnerability
- Affected
- Zyxel Multiple Network-Attached Storage (NAS) Devices
- Required action
- Apply updates per vendor instructions.
- Due date
- Ransomware use
- Unknown
- Vendors
- zyxel
- Products
- nas326 firmware, nas520 firmware, nas540 firmware, nas542 firmware, atp100 firmware, atp200 firmware, atp500 firmware, atp800 firmware, usg20-vpn firmware, usg20w-vpn firmware, usg40 firmware, usg40w firmware
- Weakness
- CWE-78
- Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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