CVE-2025-4732: Totolink A3002r Buffer Overflow Vulnerability

CVE-2025-4732 Overview

CVE-2025-4732 is a buffer overflow vulnerability in TOTOLINK A3002R and A3002RU routers running firmware version 3.0.0-B20230809.1615. The flaw resides in the HTTP POST request handler at the /boafrm/formFilter endpoint. Attackers can trigger the overflow by manipulating the ip6addr argument in a crafted POST request. The vulnerability is classified as a classic memory corruption flaw under [CWE-119]. Public disclosure of exploitation details has occurred, increasing risk to exposed devices.

Critical Impact
Remote attackers with low privileges can corrupt memory on affected TOTOLINK A3002R and A3002RU routers, potentially leading to arbitrary code execution or device compromise.

Affected Products

TOTOLINK A3002R router (hardware)
TOTOLINK A3002R firmware 3.0.0-B20230809.1615
TOTOLINK A3002RU router (hardware) and firmware 3.0.0-B20230809.1615

Discovery Timeline

2025-05-16 - CVE-2025-4732 published to NVD
2025-06-20 - Last updated in NVD database

Technical Details for CVE-2025-4732

Vulnerability Analysis

The vulnerability exists in the /boafrm/formFilter handler within the boa-based HTTP server running on TOTOLINK A3002R and A3002RU devices. The handler processes user-supplied IPv6 filter input through the ip6addr POST parameter without enforcing length validation. When an attacker submits an overly long ip6addr value, the data overruns a fixed-size buffer in the handler's stack or heap region. This corrupts adjacent memory and control structures, enabling denial of service or potential code execution on the embedded device.

The issue is categorized as a buffer overflow under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer). EPSS data indicates a moderate near-term exploitation probability, and a public proof-of-concept has been referenced through the VulDB submission.

Root Cause

The formFilter function copies the ip6addr parameter into a fixed-length buffer without validating input length against the destination size. The boa HTTP daemon used in TOTOLINK firmware passes raw POST values directly to internal handlers. The handler likely relies on unsafe string operations such as strcpy or sprintf, common in MIPS-based router firmware. No bounds checking exists before the copy operation, allowing attacker-controlled data to overflow the buffer.

Attack Vector

The attack is initiated remotely over the network against the router's HTTP management interface. The attacker requires low-privilege authenticated access to send the malicious POST request to /boafrm/formFilter. The crafted request supplies an oversized ip6addr value, triggering the overflow. Devices exposing the management interface to untrusted networks face the highest risk. See the VulDB advisory for CVE-2025-4732 and the referenced proof-of-concept notes for additional technical context.

Detection Methods for CVE-2025-4732

Indicators of Compromise

HTTP POST requests to /boafrm/formFilter containing abnormally long ip6addr parameter values
Unexpected reboots, crashes, or service restarts of the boa HTTP daemon on the router
New or unexplained outbound connections from the router to unknown infrastructure
Configuration changes to firewall, DNS, or routing tables without administrator action

Detection Strategies

Inspect web access and application logs for POST requests targeting /boafrm/formFilter with ip6addr payloads exceeding typical IPv6 address length
Deploy network intrusion detection signatures that flag oversized parameter values in router admin requests
Correlate router availability monitoring alerts with concurrent inbound HTTP traffic to the management interface

Monitoring Recommendations

Forward router syslog data to a centralized SIEM and alert on repeated HTTP 500 errors or daemon restarts
Monitor administrative interface access from non-management subnets or external IP ranges
Track outbound traffic baselines from edge routers to detect post-exploitation command-and-control activity

How to Mitigate CVE-2025-4732

Immediate Actions Required

Restrict access to the router's HTTP management interface to trusted internal hosts only and block WAN-side administration
Change default and weak administrative credentials to prevent low-privilege authenticated abuse
Audit current firmware version and inventory all TOTOLINK A3002R and A3002RU devices in the environment
Place affected devices behind a network segment with strict ACLs until a vendor patch is applied

Patch Information

At the time of NVD publication, no official vendor patch was listed in the references. Administrators should monitor the TOTOLINK official website for firmware updates addressing CVE-2025-4732. Apply any released firmware update immediately upon availability and verify integrity using vendor-provided checksums.

Workarounds

Disable remote management on the WAN interface and limit LAN management to dedicated administrative VLANs
Place affected routers behind an upstream firewall that filters HTTP traffic to /boafrm/* paths from untrusted sources
Replace end-of-life or unmaintained TOTOLINK devices with vendor-supported hardware where patches are not forthcoming

bash

# Example iptables rule to restrict router admin interface to a management subnet
iptables -A INPUT -p tcp --dport 80 -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP