Zyxel Customers Urged to Patch Exploited Bug
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2023-28771 | Unauthenticated OS Command Injection in Zyxel ATP, USG FLEX, VPN, and ZyWALL Firewalls CVE-2023-28771 is an unauthenticated OS command injection flaw (CWE-78) in Zyxel firewall firmware, caused by improper error message handling in the IKE packet decoder. A remote attacker triggers it by sending crafted packets to an affected device, with no credentials or user interaction required (CVSS 3.1: 9.8, network vector, low complexity). Successful exploitation lets the attacker execute operating-system commands on the firewall, which typically means full device compromise of these perimeter/VPN gateway appliances. Organizations running Zyxel ZyWALL/USG, VPN, USG FLEX, or ATP series firewalls on the affected firmware ranges are exposed, especially where IKE/VPN traffic is reachable from the internet. Exploitation is confirmed in the wild: the flaw was added to CISA's KEV on 2023-05-31, carries a 99.3% EPSS score (100th percentile), is reportedly used by DDoS botnets, and was reportedly exploited in the May 2023 coordinated attacks against nearly two dozen Danish energy companies. Do: Apply Zyxel's patched firmware to all affected devices per the vendor advisory - releases newer than 4.73 for ZyWALL/USG and newer than 5.35 for ATP, USG FLEX, and VPN series - prioritizing internet-facing and VPN gateway appliances, as this is a KEV required-action vulnerability. Where immediate patching is not possible, restrict IKE traffic (UDP 500/4500) to trusted peers or disable unneeded IPsec VPN termination. After patching, review device logs and configurations for signs of command execution or unexpected changes, given confirmed botnet and targeted-attack use. | 9.8 | 99% | KEV PoC |
| largetens of thousands of internet-exposed Zyxel firewall/VPN gateways (order of 10,000-100,000 devices/sites); estimate | |
| CVE-2023-33010 +1 in the same advisory: …33009 | Buffer Overflow in Zyxel ATP, USG FLEX, VPN and ZyWALL/USG Firewalls Enables RCE CVE-2023-33010 is a buffer overflow (CWE-120) in the ID processing function of Zyxel's firewall firmware that is triggered when an affected device processes crafted input sent by an unauthenticated attacker. Successful exploitation can cause denial-of-service conditions and, more seriously, allow remote code execution on the firewall itself, giving an attacker a foothold at the network perimeter. The flaw affects multiple Zyxel firewall lines widely used by small and mid-sized organizations, including ATP, USG FLEX, USG FLEX 50(W), USG20(W)-VPN, VPN, and legacy ZyWALL/USG models. The vulnerability has been added to CISA's Known Exploited Vulnerabilities catalog (added 2023-06-05), indicating it is being exploited in the wild, though no public proof-of-concept is known and ransomware association is unconfirmed. EPSS puts the 30-day exploitation probability at 28.8% (98th percentile), and no CVSS score has been published yet. Do: Apply the updated firmware for your specific model per Zyxel's security advisory, since the CISA required action is to patch per vendor instructions. Until patched, restrict or disable WAN-side access to the firewall's management/ID processing interfaces and monitor devices for signs of compromise such as unexpected reboots or crashes. Inventory all ATP, USG FLEX (including 50(W)), USG20(W)-VPN, VPN, and ZyWALL/USG units to confirm none remain unpatched. | 9.8 | 29% | KEV |
| large≈tens of thousands of internet-exposed devices from a combined installed base likely well over 100,000 across these firewall lines |
Full article330 words · extracted from infosecurity-magazine.com · click to collapse
The security community is urging Zyxel networking device users to update their firewalls and VPNs after reports that hackers are actively exploiting a vulnerability in the wild to enable remote code execution.
The Taiwanese vendor fixed CVE-2023-28771 on April 25, revealing that the flaw affects its ATP, USG Flex, VPN and ZyWall/USG products, from versions ZLD V4.60 to V5.35. In the case of the ZyWall/USG product it impacts versions ZLD V4.60 to V4.73.
“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,” Zyxel warned in its advisory.
Read more on Zyxel security risks: Over 20,000 Zyxel Firewalls Still Exposed to Critical Bug.
Rapid7 explained in a blog post yesterday that the bug is present in the default configuration of vulnerable devices and is exploitable in the Wide Area Network (WAN) interface, which is designed to be exposed to the internet.
“Successful exploitation of CVE-2023-28771 allows an unauthenticated attacker to execute code remotely on the target system by sending a specially crafted IKEv2 packet to UDP port 500 on the device,” it added.
Rapid7 warned that the CVE is being “widely exploited” to compromise devices and conscript them into a Mirai-based botnet, most likely for DDoS attacks.
In a further indication of the potential impact of the vulnerability, the US Cybersecurity and Infrastructure Security Agency (CISA) added the CVE to its Known Exploited Vulnerabilities Catalog.
That means civilian federal agencies have until June 21 to patch it, although non-government organizations are also urged to take action on any vulnerabilities listed in the catalog.
As if that weren’t enough for Zyxel customers, the firm also published an advisory for two newer vulnerabilities – CVE-2023-33009 and CVE-2023-33010 – last week. These are buffer overflow vulnerabilities that can allow unauthenticated attackers to “cause a DoS condition or execute arbitrary code on affected devices,” according to Rapid 7.
Editorial image credit: Postmodern Studio / Shutterstock.com
Text extracted automatically; images, tables and formatting may be missing. Original: https://www.infosecurity-magazine.com/news/zyxel-customers-urged-patch/