CVE-2026-9348 Overview
CVE-2026-9348 is a stack-based buffer overflow vulnerability affecting Edimax EW-7438RPn devices through firmware version 1.31. The flaw resides in the webs component, specifically in handling of the /goform/mp endpoint. Attackers can manipulate the webs argument to overflow a stack buffer and corrupt adjacent memory. The vulnerability is remotely exploitable over the network and requires only low-level privileges. A public exploit is available, increasing the likelihood of opportunistic attacks. Edimax was contacted prior to disclosure but did not respond, leaving affected devices without a vendor-supplied fix at the time of publication.
Critical Impact
Remote attackers with low privileges can trigger a stack-based buffer overflow in the embedded web server, enabling potential arbitrary code execution on the device.
Affected Products
- Edimax EW-7438RPn firmware versions up to and including 1.31
- The vulnerable webs HTTP service component
- The /goform/mp request handler
Discovery Timeline
- 2026-05-24 - CVE-2026-9348 published to the National Vulnerability Database (NVD)
- 2026-05-26 - Last updated in NVD database
Technical Details for CVE-2026-9348
Vulnerability Analysis
The vulnerability is classified under [CWE-119] as an improper restriction of operations within the bounds of a memory buffer. The flaw exists in the webs HTTP daemon embedded in the Edimax EW-7438RPn range extender. Specifically, the handler servicing requests at /goform/mp copies attacker-controlled input from the webs parameter into a fixed-size stack buffer without validating the source length. When the supplied data exceeds the destination buffer size, adjacent stack memory is overwritten, including saved return addresses and frame pointers. This corruption enables control-flow hijacking on the affected MIPS-based embedded device.
Root Cause
The root cause is missing bounds checking on the webs argument before it is written to a stack-allocated buffer inside the /goform/mp handler. The handler uses an unsafe string-copy operation without enforcing a maximum length derived from the destination buffer size. Embedded SOHO router firmware frequently lacks stack canaries, address space layout randomization (ASLR), and non-executable stack protections, making such overflows directly exploitable.
Attack Vector
Exploitation requires network access to the device's web management interface and low-privileged authenticated access. An attacker sends a crafted HTTP request to /goform/mp with an oversized value supplied through the webs parameter. The oversized payload overwrites the saved return address on the stack, redirecting execution to attacker-supplied shellcode or a return-oriented programming (ROP) chain resident in the firmware image. Successful exploitation yields code execution in the context of the webs process, which on most consumer router firmware runs as root.
No verified proof-of-concept code is reproduced here. Refer to the GitHub Vulnerability Details and VulDB #365311 for the publicly disclosed technical analysis.
Detection Methods for CVE-2026-9348
Indicators of Compromise
- HTTP POST or GET requests to /goform/mp containing abnormally long values in the webs parameter
- Crashes, reboots, or unexpected restarts of the webs HTTP daemon on the device
- Outbound connections from the router to unknown external hosts following management-plane requests
- DNS or routing table modifications applied without administrator action
Detection Strategies
- Inspect inbound HTTP traffic to router management interfaces for requests targeting /goform/mp with parameter lengths exceeding typical sizes
- Deploy network intrusion detection signatures that flag oversized webs argument values directed at Edimax management endpoints
- Correlate web management access logs with subsequent configuration changes or service restarts on the device
Monitoring Recommendations
- Restrict and log all access to the router's HTTP administrative interface from internal network segments
- Alert on repeated malformed requests to /goform/ URIs from any single source
- Monitor for new or unexpected processes, listeners, or outbound connections originating from network infrastructure devices
How to Mitigate CVE-2026-9348
Immediate Actions Required
- Remove affected Edimax EW-7438RPn devices from networks where they are exposed to untrusted users or the internet
- Disable remote management on the device and restrict the web interface to a dedicated management VLAN
- Rotate device administrative credentials, since exploitation requires low-privileged authenticated access
- Audit DNS, routing, and firewall settings on the device for unauthorized modifications
Patch Information
No vendor patch is available. Edimax did not respond to the disclosure attempt referenced in the VulDB advisory. Operators of the EW-7438RPn should monitor the Edimax support portal for firmware updates and consider replacing end-of-support hardware with actively maintained equivalents.
Workarounds
- Block external access to the device's HTTP management interface at the network perimeter
- Place the device on an isolated network segment that cannot reach sensitive internal resources
- Decommission the device and replace it with hardware that receives current security updates from the vendor
# Example: restrict access to the router management interface using iptables on an upstream gateway
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -s <trusted_admin_subnet> -j ACCEPT
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
