CVE-2026-8234: EFM ipTIME A8004T Buffer Overflow Flaw

CVE-2026-8234 Overview

CVE-2026-8234 is a stack-based buffer overflow vulnerability in the EFM ipTIME A8004T router running firmware version 14.18.2. The flaw resides in the formWifiBasicSet function within the /goform/WifiBasicSet endpoint. An attacker can manipulate the security_5g argument to overflow a fixed-size buffer on the stack. The vulnerability is remotely exploitable over the network and the exploit details have been disclosed publicly. The vendor was contacted prior to disclosure but did not respond, leaving affected devices without an official patch.

Critical Impact
Authenticated remote attackers can trigger a stack-based buffer overflow in the router's web management interface, potentially leading to memory corruption, denial of service, or arbitrary code execution on the device.

Affected Products

EFM ipTIME A8004T firmware version 14.18.2
Web management interface endpoint /goform/WifiBasicSet
The formWifiBasicSet handler function

Discovery Timeline

2026-05-10 - CVE-2026-8234 published to NVD
2026-05-13 - Last updated in NVD database

Technical Details for CVE-2026-8234

Vulnerability Analysis

The vulnerability is classified under [CWE-119] as an improper restriction of operations within the bounds of a memory buffer. The formWifiBasicSet function processes wireless configuration parameters submitted to the /goform/WifiBasicSet HTTP endpoint. When handling the security_5g parameter, the function copies attacker-controlled input into a fixed-size stack buffer without validating its length. Supplying an overly long value corrupts adjacent stack memory, including the saved return address. The attack vector is network-based and requires low privileges, with no user interaction. Successful exploitation impacts the confidentiality, integrity, and availability of the device.

Root Cause

The root cause is the absence of bounds checking on the security_5g POST parameter before it is written into a stack-allocated buffer inside formWifiBasicSet. The handler trusts the length of incoming form data, allowing the buffer to be overrun. Embedded MIPS or ARM binaries common to ipTIME devices typically lack modern stack protections such as stack canaries and ASLR, which increases the likelihood of reliable exploitation.

Attack Vector

An authenticated attacker with access to the router's web administration interface sends a crafted HTTP POST request to /goform/WifiBasicSet containing an oversized security_5g value. Because the request can be issued over the LAN or, if remote management is enabled, across the WAN, the impact extends beyond local network access. The overflow can be leveraged to crash the httpd process, causing a denial of service, or to hijack control flow and execute arbitrary code in the context of the router's web service. Public disclosure of the vulnerability details on GitHub and VulDB increases the risk of opportunistic exploitation.

// No verified proof-of-concept code is published in the references.
// See the GitHub issue and VulDB entry linked above for technical details.

Detection Methods for CVE-2026-8234

Indicators of Compromise

HTTP POST requests to /goform/WifiBasicSet containing unusually long security_5g parameter values.
Unexpected restarts or crashes of the httpd process on the router, often visible as brief web interface outages.
New or modified wireless configuration entries that do not correspond to administrator actions.
Outbound connections from the router to unknown hosts following suspicious management requests.

Detection Strategies

Inspect web server and syslog output on the device for repeated requests to /goform/WifiBasicSet from a single source.
Deploy network intrusion detection signatures that flag oversized form parameters submitted to ipTIME management endpoints.
Correlate management interface authentication events with subsequent configuration-changing requests to identify abuse of low-privileged accounts.

Monitoring Recommendations

Forward router logs to a centralized logging platform and alert on httpd crashes or watchdog-triggered reboots.
Monitor LAN segments hosting management interfaces for HTTP requests carrying parameter values exceeding expected lengths.
Track administrative logins to ipTIME devices and review session activity for anomalous configuration writes.

How to Mitigate CVE-2026-8234

Immediate Actions Required

Restrict access to the router's web management interface to trusted internal hosts using firewall rules or management VLAN isolation.
Disable remote (WAN-side) administration on the EFM ipTIME A8004T until a fix is available.
Rotate administrative credentials and enforce strong, unique passwords to limit the value of stolen low-privilege accounts.
Inventory affected devices and prioritize replacement of unsupported hardware where the vendor has not issued a patch.

Patch Information

At the time of publication, EFM Networks has not released a security patch for CVE-2026-8234. According to the disclosure, the vendor did not respond to early notification. Administrators should monitor the EFM ipTIME support portal for firmware updates and apply any future release that addresses the formWifiBasicSet handler. Refer to the VulDB entry and the GitHub disclosure for ongoing updates.

Workarounds

Block external access to TCP ports used by the router's web administration service at the network perimeter.
Place the router's management interface behind a VPN so that only authenticated remote users on a trusted network can reach /goform/WifiBasicSet.
Where possible, replace the EFM ipTIME A8004T with a supported model that receives current firmware updates.
Segment the router from sensitive internal assets to limit lateral movement in the event of compromise.

bash

# Example: restrict access to the router web UI to a trusted management subnet
# Run on an upstream firewall, replacing addresses to match your environment
iptables -A FORWARD -p tcp -s 192.0.2.0/24 -d 192.168.0.1 --dport 80 -j ACCEPT
iptables -A FORWARD -p tcp -d 192.168.0.1 --dport 80 -j DROP
iptables -A FORWARD -p tcp -d 192.168.0.1 --dport 443 -j DROP