CVE-2025-9783 Overview
CVE-2025-9783 is a buffer overflow vulnerability in the TOTOLINK A702R router running firmware version 4.0.0-B20211108.1423. The flaw resides in the sub_418030 function within the /boafrm/formParentControl endpoint. Attackers can trigger the overflow by manipulating the submit-url argument supplied to this handler. The vulnerability is exploitable remotely over the network and requires only low-privilege access. Public disclosure of the issue includes a proof-of-concept, increasing the likelihood of opportunistic exploitation against exposed devices. The weakness is classified under [CWE-119] for improper restriction of operations within the bounds of a memory buffer.
Critical Impact
Remote attackers with low-level credentials can corrupt memory on the affected router, potentially leading to arbitrary code execution or denial of service on the device.
Affected Products
- TOTOLINK A702R router hardware
- TOTOLINK A702R firmware 4.0.0-B20211108.1423
- Deployments exposing the /boafrm/formParentControl web interface
Discovery Timeline
- 2025-09-01 - CVE-2025-9783 published to NVD
- 2025-09-04 - Last updated in NVD database
Technical Details for CVE-2025-9783
Vulnerability Analysis
The vulnerability sits in the sub_418030 function of the BOA-based web management interface at /boafrm/formParentControl. The handler processes the submit-url parameter without enforcing length validation before copying it into a fixed-size stack or heap buffer. Supplying an oversized value overruns the destination buffer and corrupts adjacent memory. On embedded MIPS or ARM targets like the A702R, this class of flaw frequently enables control-flow hijacking through return-address overwrite or function-pointer corruption. A successful exploit can result in arbitrary code execution under the privileges of the web daemon, which typically runs as root on consumer routers. At minimum, the device crashes and reboots, producing denial of service. EPSS data indicates a probability of approximately 0.429 percent at the 62nd percentile.
Root Cause
The root cause is the absence of bounds checking on attacker-controlled input copied into a finite buffer. The submit-url parameter is consumed by sub_418030 without sanitization or length enforcement, matching the [CWE-119] pattern.
Attack Vector
The attack vector is network-based and targets the router's HTTP management interface. An authenticated user with low privileges sends a crafted POST request to /boafrm/formParentControl containing an oversized submit-url value. No user interaction is required beyond the request itself. Routers exposing the management interface to the WAN or to untrusted internal segments are reachable by remote adversaries.
No verified exploit code is reproduced here. The proof-of-concept is published in the GitHub repository referenced under GitHub PoC Repository and additional analysis is available at VulDB #322085 Details.
Detection Methods for CVE-2025-9783
Indicators of Compromise
- Unexpected reboots or httpd/boa process crashes on TOTOLINK A702R devices
- HTTP POST requests to /boafrm/formParentControl containing abnormally long submit-url parameter values
- Configuration changes to parental control settings not initiated by an administrator
- New outbound connections from the router to unfamiliar hosts following management-interface activity
Detection Strategies
- Inspect web server and router syslog output for repeated requests to /boafrm/formParentControl from a single source
- Apply network IDS signatures that flag oversized parameter values in POST bodies targeting BOA endpoints
- Correlate authentication events with subsequent abnormal HTTP payload sizes to surface low-privilege abuse
Monitoring Recommendations
- Forward router logs to a centralized logging platform for retention and analysis
- Alert on any administrative interface access originating from outside trusted management subnets
- Track device uptime and unexpected restarts as a proxy signal for exploitation attempts
How to Mitigate CVE-2025-9783
Immediate Actions Required
- Restrict access to the A702R web management interface to trusted internal hosts only
- Disable remote WAN-side administration if it is currently enabled
- Rotate router administrator credentials to remove low-privilege accounts that are no longer required
- Place affected devices behind a perimeter firewall that blocks inbound HTTP/HTTPS to the router
Patch Information
No vendor patch has been published in the available references at the time of NVD publication. Refer to the TOTOLink Official Website for firmware release announcements and apply updates for the A702R as soon as they become available.
Workarounds
- Segment the router onto a management VLAN that is unreachable from end-user networks
- Block external access to TCP ports 80 and 443 on the router at the upstream firewall
- Replace the affected device with a supported model if a vendor patch is not released in a timely manner
- Monitor traffic to /boafrm/formParentControl and drop requests with submit-url values exceeding a safe length using an inline proxy where feasible
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
