Researchers from TRAPA Security have discovered a critical remote code execution vulnerability affecting Zyxel Firewall, tracked as CVE-2023-28771, which can be exploited to execute arbitrary code on vulnerable devices. The vulnerability is caused by improper error message handling in various Zyxel firewall firmware versions. A remote, unauthenticated attacker can trigger the flaw by sending specially crafted packets to a vulnerable device and execute some OS commands remotely. The CVSS score for this vulnerability is 9.8.
Zyxel has released security patches to address the vulnerability and has urged its customers to install them as soon as possible. The advisory published by the vendor warns that “Improper error message handling in some firewall versions could allow an unauthenticated attacker to execute some OS commands remotely by sending crafted packets to an affected device.”
In addition to CVE-2023-28771, the company has also fixed another high-severity post-authentication command injection issue affecting some specific firewall versions, tracked as CVE-2023-27991, with a CVSS score of 8.8. This vulnerability resides in the CLI command of some Zyxel firewall firmware versions, and it can be exploited by a remote, authenticated attacker to execute some OS commands.
Furthermore, Zyxel has addressed an XSS vulnerability, tracked as CVE-2023-27990, that affects some firewall versions. An authenticated attacker with administrator privileges can store malicious scripts in a vulnerable device through this vulnerability. A successful XSS attack could then result in the stored malicious scripts being executed when the user visits the Logs page of the GUI on the device.
In summary, Zyxel has released security patches to address multiple vulnerabilities affecting various Zyxel firewall firmware versions. Customers are advised to install these patches as soon as possible to avoid any potential exploitation of these vulnerabilities.
