Wavlink WN553X1-B Router WireGuard CLI Group Handler Remote Command Injection (CVE-2026-120240)
Executive & SecOps Summary
SECOPS ASSESSMENTWavlink WN553X1-B router firmware version V260403_2.0.0 and prior
Authenticated remote attackers can execute arbitrary OS commands with root privileges by manipulating WireGuard CLI group configuration parameters
Restrict external access to the router management interface and apply the official firmware patch or implement strict input validation filters
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Monitor the vendor's official channels for the release of a patched firmware version. To upgrade the firmware via the command-line interface, use the following secure procedure:
# 1. Download the latest secure firmware image (verify the official URL from Wavlink)
wget http://firmware.wavlink.com/wn553x1b/latest_firmware.bin -O /tmp/firmware.bin
# 2. Verify the integrity of the downloaded firmware using SHA256
echo 'EXPECTED_SHA256_HASH_HERE /tmp/firmware.bin' | sha256sum -c -
# 3. Perform the system upgrade using the sysupgrade utility
sysupgrade -v /tmp/firmware.bin2. Temporary Workaround & Hardening Configuration
If a patch cannot be applied immediately, disable remote WAN access to the router's administration interface (HTTP/HTTPS/SSH) and restrict access to trusted internal IP addresses only.
# Block all incoming HTTP/HTTPS traffic on the WAN interface (e.g., eth0)
iptables -I INPUT -i eth0 -p tcp --dport 80 -j DROP
iptables -I INPUT -i eth0 -p tcp --dport 443 -j DROP
# Allow access only from a trusted administrator IP address (e.g., 192.168.1.100)
iptables -I INPUT -i eth0 -s 192.168.1.100 -p tcp --dport 443 -j ACCEPT3. Log Audit & IoC Verification Commands
Access the router's shell to verify the current firmware version and inspect system logs for any signs of command injection attempts targeting the /bin/ioos binary.
# 1. Check the active firmware version
cat /etc/openwrt_release | grep -i 'version'
# 2. Search system logs for suspicious shell metacharacters in ioos execution
logread | grep -E 'ioos.*(;|\||\&|\`|\$)'
# 3. Audit running processes for unauthorized shell instances
ps | grep -E 'sh|bash|ash' | grep -v 'grep'Stop Exposing VPN Ports to the Internet — Switch to Zero-Trust Access
Eliminate public-facing VPN concentrators and firewall management ports with identity-first Zero-Trust Network Access.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability exists in the /bin/ioos binary, specifically within the sub_41A748 function of the WireGuard CLI Group Handler component in Wavlink WN553X1-B routers. The root cause is the lack of proper input validation and sanitization on the group_id and group_name arguments before they are concatenated into a system command string. This leads to an OS Command Injection vulnerability (CWE-77/CWE-78).
2. Exploitation Mechanics & Attack Scenario
An authenticated remote attacker can exploit this vulnerability by sending a crafted request to the WireGuard CLI group configuration endpoint. By embedding shell metacharacters (such as ;, &, |, or ` `) into the group_id or group_name parameters, the attacker can break out of the intended command context. The /bin/ioos` binary executes the resulting string via a system shell, allowing the attacker to run arbitrary commands with elevated privileges.
3. Infrastructure & Business Impact
With a CVSS score of 9.9 (Critical), this vulnerability poses a severe threat to network infrastructure. Successful exploitation grants the attacker full control over the router. This can lead to unauthorized access to internal networks, traffic interception, DNS hijacking, or enrollment of the compromised device into a malicious botnet.
Official Vendor Advisories & References
A vulnerability was determined in WAVLINK WN553X1-B V260403_2.0.0. This issue affects the function sub_41A748 of the file /bin/ioos of the component WireGuard CLI Group Handler. Executing a manipulation of the argument group_id/group_name can lead to os command injection. The attack may be performed from remote. The exploit has been publicly disclosed and may be utilized. The vendor was contacted early about this disclosure.
Frequently Asked SecOps Questions (CVE-2026-120240)
FAQQ1. How critical is CVE-2026-120240 and is it actively exploited in the wild?
CVE-2026-120240 is rated CVSS 9.9 (CRITICAL) with a 30-day EPSS exploitation probability of 1.7%. Organizations running affected versions should prioritize patching based on network exposure.
Q2. Which vendors and products are affected by CVE-2026-120240?
Primary impacted vendors include wavlink across wn553x1-b. Scope summary: Wavlink WN553X1-B router firmware version V260403_2.0.0 and prior
Q3. What temporary mitigations or workarounds exist for CVE-2026-120240 before patching?
[Mitigation] Restrict external access to the router management interface and apply the official firmware patch or implement strict input validation filters Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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