There is an IT security warning for Zyxel Firewalls. Here you can find out which vulnerabilities are involved, which products are affected and what you can do.
The latest manufacturer recommendations regarding updates, workarounds and security patches for this vulnerability can be found here: CISA Alert (Status: 01.06.2023). Other useful sources are listed later in this article.
Security Advisory for Zyxel Firewalls – Critical Risk
Risk level: 4 (critical)
CVSS Base Score: 9,8
CVSS Temporal Score: 9,4
Remoteangriff: Ja
The Common Vulnerability Scoring System (CVSS) is used to assess the vulnerability of computer systems. The CVSS standard makes it possible to compare potential or actual security vulnerabilities based on various criteria in order to better prioritize countermeasures. The attributes “none”, “low”, “medium”, “high” and “critical” are used for the severity of a vulnerability. The base score assesses the prerequisites for an attack (including authentication, complexity, privileges, user interaction) and its consequences. The Temporal Score also takes into account changes over time with regard to the risk situation. The risk of the vulnerability discussed here is rated as “critical” according to the CVSS with a base score of 9.8.
Zyxel Firewalls Bug: Description of the attack
Zyxel is a manufacturer of network components, including firewalls.
An attacker could exploit multiple vulnerabilities in Zyxel Firewall to execute arbitrary code, disclose information, cause a denial of service, perform a cross-site scripting attack, or manipulate the configuration.
The vulnerabilities were classified using the CVE reference system (Common Vulnerabilities and Exposures) based on the individual serial numbers CVE-2023-28771, CVE-2023-27991, CVE-2023-27990, CVE-2023-22918, CVE-2023-22917, CVE-2023-22916, CVE-2023-22915, CVE-2023-22914 und CVE-2023-22913.
Systems affected by the vulnerability at a glance
operating system
Products
Zyxel Firewall < ZLD V5.36 (cpe:/h:zyxel:firewall)
Zyxel Firewall < ZLD V4.73 Patch 1 (cpe:/h:zyxel:firewall)
General measures to deal with IT vulnerabilities
- Users of the affected systems should keep them up to date. When security vulnerabilities become known, manufacturers are required to remedy them as quickly as possible by developing a patch or a workaround. If security patches are available, install them promptly.
- For information, consult the sources listed in the next section. These often contain further information on the latest version of the software in question and the availability of security patches or tips on workarounds.
- If you have any further questions or are uncertain, please contact your responsible administrator. IT security managers should regularly check when the manufacturing company makes a new security update available.
Sources for updates, patches and workarounds
At this point there are further links with information about bug reports, security fixes and workarounds.
CISA Alert from 2023-06-01 (02.06.2023)
For more information, see: https://www.cisa.gov/news-events/alerts/2023/05/31/cisa-adds-one-known-exploited-vulnerability-catalog
PoC on AttackerKB from 2023-05-22 (23.05.2023)
For more information, see: https://attackerkb.com/topics/N3i8dxpFKS/cve-2023-28771/rapid7-analysis
Zyxel Security Advisory vom 2023-04-24 (25.04.2023)
For more information, see: https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-vulnerabilities-of-firewalls-and-aps
Zyxel Security Advisory vom 2023-04-24 (25.04.2023)
For more information, see: https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-remote-command-injection-vulnerability-of-firewalls
Zyxel Security Advisory vom 2023-04-24 (25.04.2023)
For more information, see: https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-xss-vulnerability-and-post-authentication-command-injection-vulnerability-in-firewalls
Version history of this security alert
This is the 3rd version of this IT Security Notice for Zyxel Firewalls. If further updates are announced, this text will be updated. You can understand the changes made using the following version history.
04/25/2023 – Initial version
05/23/2023 – PoC added
06/02/2023 – CVE-2023-28771 actively exploited
+++ Editorial note: This text was created with AI support based on current BSI data. We accept feedback and comments at [email protected]. +++
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