9.8 High
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
10 High
CVSS2
Access Vector
NETWORK
Access Complexity
LOW
Authentication
NONE
Confidentiality Impact
COMPLETE
Integrity Impact
COMPLETE
Availability Impact
COMPLETE
AV:N/AC:L/Au:N/C:C/I:C/A:C
0.969 High
EPSS
Percentile
99.7%
Multiple ZyXEL devices contain a pre-authentication command injection vulnerability, which may allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable device.
CWE-78: Improper Neutralization of Special Elements used in an OS Command (โOS Command Injectionโ)
Multiple ZyXEL 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, many 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.
Exploit code for this vulnerability that targets NAS devices is available on the internet. For this reason, we have created a PoC exploit that has the ability to power down affected ZyXEL NAS devices.
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.
Apply an update
ZyXEL has made firmware updates available for NAS326, NAS520, NAS540, NAS542, ATP100, ATP200, ATP500, ATP800, USG20-VPN, USG20W-VPN, USG40, USG40W, USG60, USG60W, USG110, USG210, USG310, USG1100, USG1900, USG2200, VPN50, VPN100, VPN300, VPN1000, ZyWALL110, ZyWALL310, and ZyWALL1100 devices. Owners of NSA210, NSA220, NSA220+, NSA221, NSA310, NSA310S, NSA320, NSA320S, NSA325 and NSA325v2 as well as some other ZyXEL devices may not be able to install firmware updates, as these devices are no longer supported. Be cautious when updating firmware on affected devices, as the ZyXEL firmware upgrade process both uses an insecure channel (FTP) for retrieving updates, and the firmware files are only verified by checksum rather than cryptographic signature. For these reasons, any attacker that has control of DNS or IP routing may be able to cause a malicious firmware to be installed on a ZyXEL device.
Please also consider the following workarounds:
Block access to the ZyXEL device web interface
This issue can be mitigated by blocking (for example with a firewall) access to the web interface (80/tcp and 443/tcp) of any vulnerable ZyXEL device. Any machine that can access the ZyXEL web interface should not also be able to access the internet.
Restrict access to vulnerable ZyXEL devices
Direct exploitation of this vulnerability can be mitigated by restricting access to vulnerable devices. In particular, do not expose such devices directly to the internet. Note however, that it is still possible for attackers to exploit devices that are not directly connected to the internet. For example, by way of viewing a web page.
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Notified: February 15, 2020 Updated: February 24, 2020
Affected
We have not received a statement from the vendor.
We are not aware of further vendor information regarding this vulnerability.
Group | Score | Vector |
---|---|---|
Base | 10 | AV:N/AC:L/Au:N/C:C/I:C/A:C |
Temporal | 9.5 | E:F/RL:U/RC:C |
Environmental | 7.1 | CDP:ND/TD:M/CR:ND/IR:ND/AR:ND |
Thanks to Brian Krebs for notifying us of the exploit availability, which was uncovered by Alex Holden of Hold Security.
This document was written by Will Dormann.
CVE IDs: | CVE-2020-9054 |
---|---|
Date Public: | 2020-02-12 Date First Published: |
9.8 High
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
10 High
CVSS2
Access Vector
NETWORK
Access Complexity
LOW
Authentication
NONE
Confidentiality Impact
COMPLETE
Integrity Impact
COMPLETE
Availability Impact
COMPLETE
AV:N/AC:L/Au:N/C:C/I:C/A:C
0.969 High
EPSS
Percentile
99.7%