CVE-2026-7255 Overview
CVE-2026-7255 is an improper restriction of excessive authentication attempts vulnerability [CWE-307] in the web management interface of the Zyxel WRE6505 v2 wireless range extender. The flaw affects firmware version V1.00(ABDV.3)C0 and allows an adjacent attacker on the local area network (LAN) to brute-force the administrator password and bypass authentication. Zyxel has marked this device as unsupported at the time of CVE assignment, meaning no security patch will be released. The vulnerability carries a CVSS 3.1 score of 6.5 and an EPSS probability of 0.019%.
Critical Impact
An adjacent LAN attacker can brute-force administrator credentials on an end-of-life device that will not receive a vendor patch, leading to full compromise of the web management interface.
Affected Products
- Zyxel WRE6505 v2 hardware (end-of-life)
- Zyxel WRE6505 firmware version V1.00(ABDV.3)C0
- Web management interface component of the device
Discovery Timeline
- 2026-05-12 - CVE CVE-2026-7255 published to NVD
- 2026-05-13 - Last updated in NVD database
Technical Details for CVE-2026-7255
Vulnerability Analysis
The Zyxel WRE6505 v2 web management interface fails to enforce rate limiting or account lockout on failed authentication attempts. An attacker positioned on the same LAN segment can submit unlimited login requests against the administrative interface. Without throttling, automated tools can iterate through password dictionaries or perform pure brute-force enumeration in a short timeframe.
Successful authentication grants the attacker full administrative control of the device. From this position, the attacker can modify wireless settings, alter DNS configurations, capture client traffic, or pivot further into the local network. Because the WRE6505 v2 acts as a wireless range extender, compromise extends to every client that associates with the extended SSID.
The vendor has classified the product as end-of-life. No firmware update will be issued to address this issue, making decommissioning the only complete remediation. The advisory directs operators to the Zyxel End of Life Support page.
Root Cause
The underlying weakness is a missing authentication attempt counter in the HTTP login handler. The interface does not track failed logins per source IP, per account, or globally. It does not introduce delays between attempts or trigger temporary lockouts after a threshold. This maps directly to CWE-307: Improper Restriction of Excessive Authentication Attempts.
Attack Vector
Exploitation requires network adjacency, which means the attacker must reside on the same LAN or wireless segment as the device. An attacker who has joined the guest or extended wireless network can reach the management interface directly. The attack requires no privileges and no user interaction. Brute-force tools such as Hydra or custom scripts can target the HTTP login endpoint and iterate credentials until authentication succeeds.
No verified proof-of-concept code is published for this CVE. The exploitation pattern is a standard online password guessing attack against an HTTP form.
Detection Methods for CVE-2026-7255
Indicators of Compromise
- High volumes of HTTP POST requests to the WRE6505 web management login endpoint from a single LAN host within a short window.
- Successful administrative login from an unfamiliar internal IP address or at unusual hours.
- Unexpected configuration changes on the WRE6505, including modified SSIDs, DNS servers, or admin passwords.
- New or unknown wireless clients associating shortly after configuration changes.
Detection Strategies
- Mirror or span LAN traffic destined for the WRE6505 management IP and alert on repeated authentication failures.
- Deploy network detection rules that flag bursts of HTTP requests to embedded device management endpoints from non-administrative hosts.
- Correlate device configuration changes with prior authentication patterns to surface anomalies.
Monitoring Recommendations
- Forward LAN switch flow records and wireless controller logs to a centralized analytics platform for baseline and anomaly review.
- Track administrative session sources for the device and alert when a new source IP authenticates successfully.
- Monitor DHCP and ARP tables for unexpected clients on segments that host end-of-life network equipment.
How to Mitigate CVE-2026-7255
Immediate Actions Required
- Decommission the Zyxel WRE6505 v2 and replace it with a supported wireless range extender that receives security updates.
- Isolate the device on a dedicated VLAN with no access to sensitive systems until replacement is complete.
- Restrict management interface access to a single administrative host using switch ACLs or firewall rules.
- Set a long, random administrator password to increase brute-force cost while replacement is pending.
Patch Information
No patch is available. Zyxel lists the WRE6505 v2 as end-of-life and will not issue firmware updates for this product. Refer to the Zyxel End of Life Support page for product lifecycle status and replacement guidance.
Workarounds
- Block inbound TCP/80 and TCP/443 to the device from all LAN hosts except a designated management workstation.
- Disable remote management entirely if the feature is not required for daily operation.
- Segment the wireless extender onto an isolated SSID and VLAN that cannot reach corporate or sensitive resources.
- Rotate the administrative password to a high-entropy value of at least 20 characters.
# Example: restrict access to the WRE6505 management interface using iptables on an upstream gateway
# Replace 192.0.2.10 with your admin workstation IP and 192.0.2.50 with the WRE6505 IP
iptables -A FORWARD -s 192.0.2.10 -d 192.0.2.50 -p tcp --dport 80 -j ACCEPT
iptables -A FORWARD -s 192.0.2.10 -d 192.0.2.50 -p tcp --dport 443 -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.
