CVE-2025-4897: Tenda A15 Buffer Overflow Vulnerability

CVE-2025-4897 Overview

CVE-2025-4897 is a buffer overflow vulnerability affecting Tenda A15 routers running firmware versions 15.13.07.09 and 15.13.07.13. The flaw resides in the HTTP POST request handler for the /goform/multimodalAdd endpoint. Attackers can manipulate input parameters to overflow a fixed-size buffer in the device's web management interface. The vulnerability is remotely exploitable and has been publicly disclosed, increasing the risk of opportunistic attacks against exposed devices. The issue maps to [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer) and [CWE-120] (Classic Buffer Overflow).

Critical Impact
Remote attackers with low-privileged access can trigger memory corruption against the router's HTTP service, leading to denial of service or potential arbitrary code execution on the device.

Affected Products

Tenda A15 hardware (consumer wireless router)
Tenda A15 firmware version 15.13.07.09
Tenda A15 firmware version 15.13.07.13

Discovery Timeline

2025-05-18 - CVE-2025-4897 published to NVD
2025-05-27 - Last updated in NVD database

Technical Details for CVE-2025-4897

Vulnerability Analysis

The vulnerability exists in the request handling logic for /goform/multimodalAdd, a CGI-style endpoint exposed by the router's embedded HTTP server. The handler processes attacker-supplied POST parameters and copies them into a stack or heap buffer without enforcing length boundaries. Because the firmware runs on a memory-constrained embedded Linux platform with limited mitigations, overflowing the destination buffer can corrupt adjacent memory structures, including saved return addresses and function pointers. The Exploit Prediction Scoring System assigns this CVE a probability of 1.028%, ranking it in the 77th percentile of disclosed vulnerabilities, reflecting moderate near-term exploitation likelihood.

Root Cause

The root cause is missing input length validation on parameters processed by the multimodalAdd form handler. Tenda's firmware uses fixed-size local buffers and relies on unsafe string copy operations common in MIPS-based router code. When user-controlled data exceeds the expected length, the runtime overwrites adjacent memory. The condition matches the classic CWE-120 pattern: copying input to an output buffer without checking the size of the input.

Attack Vector

An authenticated attacker on the network sends a crafted HTTP POST request to /goform/multimodalAdd with oversized parameter values. The request travels across the network attack surface, requires only low privileges, and needs no user interaction. Successful exploitation yields full compromise of the device's confidentiality, integrity, and availability scope. Because the public proof of concept describes the exploitation primitive, attackers can readily adapt it. See the GitHub PoC Repository and the VulDB entry #309453 for technical details.

Detection Methods for CVE-2025-4897

Indicators of Compromise

Anomalous HTTP POST requests targeting /goform/multimodalAdd with unusually large parameter values or non-printable bytes.
Repeated crashes, reboots, or watchdog resets of the router's HTTP management daemon (httpd).
Unexpected outbound connections from the router after receipt of suspicious management traffic.
Configuration changes on the device without corresponding administrator activity.

Detection Strategies

Inspect web access logs and network captures for POST requests to /goform/multimodalAdd with parameter lengths beyond reasonable bounds.
Deploy IDS/IPS signatures that flag oversized form parameters destined for Tenda management endpoints on TCP/80 and TCP/443.
Correlate device crash events with preceding HTTP traffic to identify exploitation attempts.

Monitoring Recommendations

Forward router syslog and management-plane telemetry to a centralized SIEM for behavioral analysis.
Alert on management-interface exposure to untrusted networks, including WAN-facing administration.
Track firmware version inventory across deployed Tenda devices to identify unpatched units.

How to Mitigate CVE-2025-4897

Immediate Actions Required

Restrict access to the router's web management interface to trusted internal hosts only and disable WAN-side administration.
Change default administrative credentials and enforce strong passwords to limit the low-privilege precondition required for exploitation.
Segment Tenda A15 devices onto isolated management VLANs and block inbound HTTP/HTTPS to the device from untrusted networks.
Monitor the Tenda Official Website for firmware updates addressing the multimodalAdd handler.

Patch Information

At the time of NVD publication, no vendor advisory or patched firmware build is listed for CVE-2025-4897. Administrators should track Tenda's support portal for an updated firmware release superseding 15.13.07.13 and apply it as soon as available. Until a fix is published, compensating network controls are the primary defense.

Workarounds

Disable remote management features on the WAN interface to remove external exposure of the vulnerable endpoint.
Place the router behind an upstream firewall that filters HTTP requests targeting /goform/multimodalAdd.
Replace affected devices with supported alternatives in high-risk environments where exposure cannot be reduced.

bash

# Example: block external access to the Tenda management interface
# Adjust interface names and addresses to match your environment
iptables -A FORWARD -p tcp -d 192.0.2.10 --dport 80 -j DROP
iptables -A FORWARD -p tcp -d 192.0.2.10 --dport 443 -j DROP