CVE-2026-7256 Overview
CVE-2026-7256 is a command injection vulnerability in the Common Gateway Interface (CGI) program of the Zyxel WRE6505 v2 wireless range extender. The flaw affects firmware version V1.00(ABDV.3)C0, which Zyxel marks as end-of-life and no longer supports. An adjacent attacker on the same Local Area Network (LAN) can send a crafted HTTP request to execute arbitrary operating system (OS) commands on the device. The vulnerability is classified under CWE-78, Improper Neutralization of Special Elements used in an OS Command.
Critical Impact
Successful exploitation grants attackers OS command execution on the device, enabling full compromise of the wireless range extender and pivoting into the internal network.
Affected Products
- Zyxel WRE6505 v2 hardware
- Zyxel WRE6505 firmware version V1.00(ABDV.3)C0
- End-of-life Zyxel range extenders without vendor support
Discovery Timeline
- 2026-05-12 - CVE-2026-7256 published to the National Vulnerability Database (NVD)
- 2026-05-16 - Last updated in NVD database
Technical Details for CVE-2026-7256
Vulnerability Analysis
The vulnerability resides in a CGI program exposed by the WRE6505 v2 web management interface. The CGI handler passes attacker-controlled input from an HTTP request into an OS command without proper sanitization or neutralization of shell metacharacters. An attacker on the adjacent network can append shell operators such as ;, |, or backticks to inject additional commands that execute under the privileges of the web server process, typically root on embedded Zyxel devices.
The attack requires no authentication and no user interaction, but the attacker must hold network adjacency, meaning a position on the same LAN or Wi-Fi segment as the device. Because range extenders frequently sit on trusted internal segments, a foothold on any wireless client is sufficient to reach the management interface.
The EPSS score is 0.832% at the 74.786 percentile, indicating elevated exploitation probability compared with the broader CVE population.
Root Cause
The root cause is improper input validation in CGI request handling, mapped to [CWE-78]. The CGI program constructs an OS command string by concatenating attacker-supplied HTTP parameters directly into a shell invocation, rather than using argument arrays or strict allow-lists. Because Zyxel has placed this product in end-of-life status, no patched firmware will be released.
Attack Vector
An adjacent attacker sends a crafted HTTP request to the vulnerable CGI endpoint on the WRE6505 v2. The request includes shell metacharacters within a parameter consumed by the device command pipeline. The CGI program executes the injected commands with the privileges of the web service, granting persistent control over the extender, traffic interception capabilities, and a launch point for lateral movement.
No verified exploit code or proof-of-concept has been published. Refer to the Zyxel End of Life Support page for product status confirmation.
Detection Methods for CVE-2026-7256
Indicators of Compromise
- Unexpected HTTP POST or GET requests to CGI endpoints on the WRE6505 v2 management interface containing shell metacharacters such as ;, &&, |, or backticks
- Outbound connections from the range extender to unfamiliar IP addresses, including tunneling or reverse shell traffic
- Configuration changes, new administrative accounts, or modified DNS settings on the device that were not made by an administrator
Detection Strategies
- Inspect network traffic destined for the WRE6505 v2 web interface using an intrusion detection system (IDS) with signatures for command injection patterns in HTTP parameters
- Correlate authentication logs and DHCP records to identify wireless clients that initiate management traffic against range extenders
- Audit firmware versions across the wireless fleet and flag any device running V1.00(ABDV.3)C0 as end-of-life and at risk
Monitoring Recommendations
- Forward syslog and HTTP access logs from network infrastructure into a central SIEM or data lake for query-based hunting on CGI request anomalies
- Monitor for sudden changes in DNS responses or default gateway behavior originating from segments serviced by the extender
- Alert on any new device behavior such as outbound SSH, IRC, or non-standard high port connections from the WRE6505 v2 IP address
How to Mitigate CVE-2026-7256
Immediate Actions Required
- Decommission and replace the Zyxel WRE6505 v2 because the product is end-of-life and will not receive a security patch
- Isolate any remaining WRE6505 v2 devices on a dedicated VLAN with no access to sensitive internal resources until replacement
- Restrict access to the device web management interface to a single administrative host using firewall rules
Patch Information
Zyxel has not released and will not release a patch for CVE-2026-7256. The WRE6505 v2 is listed on the Zyxel End of Life Support page, which confirms that the model is no longer eligible for security updates. Migration to a currently supported Zyxel model or equivalent vendor product is the only durable remediation.
Workarounds
- Disable remote management and restrict the management interface to wired administrative access only
- Change default credentials and enforce strong administrator passwords to raise the cost of post-exploitation persistence
- Segment guest and IoT wireless networks away from the extender management plane using VLANs and access control lists
# Example firewall rule to restrict WRE6505 management access to a single admin host
# Replace 192.0.2.10 with the administrator workstation IP
# Replace 192.0.2.50 with the WRE6505 v2 device IP
iptables -A FORWARD -s 192.0.2.10 -d 192.0.2.50 -p tcp --dport 80 -j ACCEPT
iptables -A FORWARD -d 192.0.2.50 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.0.2.50 -p tcp --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
