CVE-2025-5739 Overview
CVE-2025-5739 is a buffer overflow vulnerability affecting TOTOLINK X15 routers running firmware version 1.0.0-B20230714.1105. The flaw resides in the HTTP POST request handler within /boafrm/formSaveConfig, where the submit-url argument is processed without proper bounds checking. Attackers can manipulate this argument to overflow the buffer and corrupt adjacent memory. The vulnerability is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer) and is exploitable remotely over the network. Public disclosure of the exploit details has occurred, increasing the risk of opportunistic exploitation 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 denial of service on the affected device.
Affected Products
- TOTOLINK X15 router (hardware)
- TOTOLINK X15 firmware version 1.0.0-B20230714.1105
- Deployments exposing the HTTP management interface to untrusted networks
Discovery Timeline
- 2025-06-06 - CVE-2025-5739 published to NVD
- 2025-06-17 - Last updated in NVD database
Technical Details for CVE-2025-5739
Vulnerability Analysis
The vulnerability resides in the formSaveConfig handler exposed under the /boafrm/ URI path on the TOTOLINK X15 web administration interface. This handler processes HTTP POST requests used to persist device configuration changes. When the handler reads the submit-url parameter from the request body, it copies the attacker-supplied value into a fixed-size stack or global buffer without validating the input length.
Because the affected firmware ships on a router accessible over the network, an attacker who can reach the HTTP service and supply low-privilege credentials can trigger memory corruption. The result is overwritten memory adjacent to the destination buffer, which on embedded MIPS or ARM targets typically corrupts saved return addresses or function pointers. Public disclosure of the exploit increases exposure for unpatched devices. The EPSS score of 1.67% (82nd percentile) reflects elevated likelihood of exploitation activity compared to the broader CVE population.
Root Cause
The root cause is missing length validation on the submit-url POST parameter inside the formSaveConfig routine of the boa web server binary. The handler relies on unsafe string copy semantics rather than bounded operations, mapping directly to [CWE-119].
Attack Vector
An attacker sends a crafted HTTP POST request to /boafrm/formSaveConfig containing an oversized submit-url value. Network reachability to the management interface and valid low-privilege authentication are required. Successful exploitation corrupts process memory in the embedded web server, enabling denial of service or potential code execution within the router's privileged context. See the GitHub CVE Documentation and VulDB CVE Analysis #311265 for technical references.
Detection Methods for CVE-2025-5739
Indicators of Compromise
- HTTP POST requests to /boafrm/formSaveConfig containing abnormally long submit-url parameter values
- Unexpected reboots, watchdog resets, or crashes of the TOTOLINK X15 boa web server process
- Configuration changes, DNS modifications, or new administrative sessions originating from untrusted source IPs
- Outbound connections from the router to unknown command-and-control infrastructure following management-plane activity
Detection Strategies
- Inspect HTTP traffic destined for router management interfaces and flag POST bodies where submit-url exceeds a reasonable length threshold such as 256 bytes
- Correlate web-management POST requests with subsequent device availability loss to surface exploitation attempts
- Apply intrusion detection signatures matching oversized parameters in /boafrm/ URI paths
Monitoring Recommendations
- Forward router syslog and HTTP access logs to a centralized analytics platform for retention and query
- Alert on authentication events to the X15 web UI from non-administrative source ranges
- Baseline normal management-plane traffic volume and alert on sudden spikes consistent with brute-force or fuzzing activity
How to Mitigate CVE-2025-5739
Immediate Actions Required
- Restrict access to the X15 web administration interface to trusted management VLANs and block WAN-side access entirely
- Disable remote HTTP management on the device until a firmware fix is available from TOTOLINK
- Rotate administrative credentials and enforce strong, unique passwords to limit the low-privilege foothold required for exploitation
- Inventory deployed TOTOLINK X15 units and confirm firmware version against 1.0.0-B20230714.1105
Patch Information
At the time of NVD publication, no vendor advisory or patched firmware release has been associated with this CVE. Monitor the Totolink Security Information page and VulDB #311265 for updated firmware availability. Apply vendor-supplied firmware as soon as it is released.
Workarounds
- Place the router behind a network segment that filters inbound HTTP and HTTPS traffic to the management interface
- Deploy a web application firewall or upstream proxy that enforces length limits on POST parameters destined for /boafrm/ endpoints
- Consider replacing end-of-life or unpatched consumer-grade hardware with vendor-supported alternatives where business risk warrants
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
