Unauthenticated Command Injection in Zyxel ZyWALL/USG, USG FLEX, ATP, and VPN Series
CVE-2023-28771 is a remote command injection vulnerability affecting Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60 through 5.35, and ATP series firmware versions 4.60 through 5.35. The vendor description attributes the issue to improper error message handling. By sending crafted packets to an affected device, an unauthenticated remote attacker can cause the device to execute operating system commands. Supporting context indicates exploitation occurs over UDP port 500 and the issue has been widely described as a command injection flaw in Zyxel firewall/VPN appliances.
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Impact, mitigation & remediation
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Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
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Remediation
Patch, then assume compromise.
Exploits
1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos (1 hidden).
This repository provides a proof-of-concept exploit for CVE-2023-28771, a command injection vulnerability affecting Zyxel firewall and VPN devices. The main file, 'CVE-2023-28771-poc.py', is a Python script that uses the Scapy library to craft and send a malicious IKEv2 packet to a specified target (rhost) on UDP port 500. The script allows the user to either execute an arbitrary shell command on the target device (using the --cmd argument) or spawn a reverse shell back to the attacker's machine (using --lhost and --lport arguments). The payload is embedded in the Notify payload of the IKEv2 packet. The repository also includes a README.md with usage instructions and a requirements.txt specifying the Scapy dependency. The exploit is operational and can be used to gain remote code execution on vulnerable Zyxel devices exposed to the internet.
Affected products & vendors
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
31 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A critical improper error message handling vulnerability in Zyxel firewall and VPN devices, allowing unauthenticated remote OS command execution via crafted packets.
A previously disclosed Zyxel firewall vulnerability involving improper error handling that can lead to remote code execution.
A Zyxel firewall vulnerability (exploitable over UDP/500) that is seeing exploit attempts and has publicly available exploit code (Metasploit), making unpatched internet-exposed devices high risk.
A 2023 vulnerability affecting Zyxel routers that is seeing a spike in attack activity, per GreyNoise.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.