CVE-2026-90607: Totolink A3002MU Buffer Overflow Vulnerability

CVE-2026-90607 Overview

CVE-2026-90607 is a buffer overflow vulnerability in the Totolink A3002MU router running firmware version Hh-B20211125.1046. The flaw resides in the formNewSchedule function within the /boafrm/formNewSchedule endpoint of the boa web server component. Attackers can trigger the overflow by manipulating the submit-url argument over the network. Public exploit details are available, increasing the likelihood of opportunistic attacks against exposed devices.

Critical Impact
Remote attackers with low-privilege access can overflow a memory buffer in the router's web management interface, potentially leading to arbitrary code execution or device compromise on affected Totolink A3002MU devices.

Affected Products

Totolink A3002MU router
Firmware version Hh-B20211125.1046
The boa web server component (/boafrm/formNewSchedule handler)

Discovery Timeline

2026-09-14 - CVE-2026-90607 published to the National Vulnerability Database (NVD)
2026-09-14 - Last updated in NVD database

Technical Details for CVE-2026-90607

Vulnerability Analysis

The vulnerability is classified as a buffer overflow [CWE-119] within the formNewSchedule handler of the embedded boa HTTP server. When an authenticated user submits a request to /boafrm/formNewSchedule, the router copies the value of the submit-url parameter into a fixed-size buffer without validating the input length. An oversized value overwrites adjacent memory, corrupting the process stack or heap depending on allocation context.

Successful exploitation can crash the boa daemon, disrupt router management, or allow attackers to hijack control flow on the MIPS-based device. Because the boa server typically runs with elevated privileges on embedded routers, code execution grants full control over network traffic passing through the device.

Root Cause

The root cause is missing bounds checking on the submit-url argument inside the formNewSchedule function. The handler uses an unsafe string copy operation that trusts attacker-controlled HTTP form data. This pattern is common in older embedded web stacks where input validation is deferred to the caller.

Attack Vector

The attack is executed remotely over the network against the router's HTTP management interface. Low-privilege credentials are required to reach the vulnerable form handler. No user interaction is needed once the request is crafted. A public proof-of-concept documenting the overflow is hosted on GitHub, lowering the barrier to exploitation. See the GitHub BoF PoC Document and the VulDB CVE-2026-90607 Entry for technical details.

No verified exploitation code is reproduced here. Refer to the linked PoC document for the raw request structure.

Detection Methods for CVE-2026-90607

Indicators of Compromise

HTTP POST requests to /boafrm/formNewSchedule containing unusually long submit-url parameter values
Repeated crashes or restarts of the boa web server process on the Totolink A3002MU
Unexpected outbound connections from the router to unknown IP addresses following administrative requests
New or modified configuration entries that were not initiated by an administrator

Detection Strategies

Inspect web management logs for requests to formNewSchedule with parameter lengths exceeding typical URL sizes (for example, more than 256 bytes)
Monitor network intrusion detection systems (NIDS) for HTTP traffic patterns targeting /boafrm/ endpoints from external sources
Baseline normal administrative traffic to the router and alert on anomalous parameter payloads

Monitoring Recommendations

Restrict router management interfaces to trusted management VLANs and log all access attempts
Forward router syslog data to a central log platform to correlate crash events with inbound HTTP traffic
Alert on repeated authentication events followed by malformed form submissions

How to Mitigate CVE-2026-90607

Immediate Actions Required

Disable remote (WAN-side) access to the router's HTTP administrative interface
Restrict LAN-side management access to a dedicated administrative subnet
Rotate router administrator credentials and enforce strong, unique passwords
Segment the affected device away from sensitive internal networks until a fix is available

Patch Information

At the time of publication, no vendor patch has been referenced in the NVD entry for CVE-2026-90607. Administrators should monitor the Totolink Official Website for firmware updates addressing the formNewSchedule handler. If the affected model is end-of-life, plan replacement with a supported device.

Workarounds

Block external access to TCP ports used by the router web interface at the perimeter firewall
Apply access control lists (ACLs) that limit /boafrm/ endpoint access to specific administrative IP addresses
Consider deploying the router behind a reverse proxy or VPN that terminates management traffic before it reaches the device

bash

# Example: restrict router HTTP admin access to a management host using iptables
iptables -A INPUT -p tcp --dport 80 -s 192.0.2.10 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP