CVE-2025-6734 Overview
CVE-2025-6734 is a buffer overflow vulnerability in the UTT HiPER 840G router firmware up to version 3.1.1-190328. The flaw resides in the sub_484E40 function handling requests to the /goform/formP2PLimitConfig API endpoint. Attackers can manipulate the except argument to trigger memory corruption over the network. The exploit has been publicly disclosed, and the vendor did not respond to disclosure attempts. The vulnerability is classified under [CWE-119] for improper restriction of operations within memory buffer bounds.
Critical Impact
Authenticated remote attackers can corrupt memory on affected UTT HiPER 840G devices, potentially leading to arbitrary code execution or denial of service on edge network equipment.
Affected Products
- UTT HiPER 840G hardware (version 3.0)
- UTT 840G firmware up to 3.1.1-190328
- Deployments exposing the /goform/formP2PLimitConfig web management interface
Discovery Timeline
- 2025-06-26 - CVE-2025-6734 published to NVD
- 2026-01-08 - Last updated in NVD database
Technical Details for CVE-2025-6734
Vulnerability Analysis
The vulnerability resides in the sub_484E40 function of the UTT HiPER 840G web management API. This function processes the formP2PLimitConfig form, which configures peer-to-peer traffic limits. Attackers reach the vulnerable code path by submitting a crafted HTTP request to /goform/formP2PLimitConfig with a malicious except parameter value. The function fails to validate the length of the supplied data before copying it into a fixed-size buffer, triggering a classic stack or heap buffer overflow [CWE-119]. Because the device runs the web service with elevated privileges, successful exploitation can compromise the entire router. The attack requires network access and low-level authentication but no user interaction.
Root Cause
The root cause is missing bounds checking on the except argument within sub_484E40. The function copies attacker-controlled input into a finite memory region without validating input length against the destination buffer size, allowing adjacent memory to be overwritten.
Attack Vector
The attack vector is remote over the network, targeting the device's HTTP-based management interface. An attacker with access to the management interface sends a POST request to /goform/formP2PLimitConfig containing an oversized except parameter. The overflow can corrupt control data on the stack or heap, enabling denial of service or arbitrary code execution depending on memory layout and mitigations present on the embedded device.
No verified proof-of-concept code is reproduced here. Technical details and a public PoC are referenced in the GitHub CVE Documentation and VulDB CVE Analysis #314009.
Detection Methods for CVE-2025-6734
Indicators of Compromise
- HTTP POST requests to /goform/formP2PLimitConfig containing unusually long except parameter values
- Unexpected reboots, crashes, or watchdog resets on UTT HiPER 840G devices
- Configuration changes to P2P traffic policies that were not initiated by administrators
- New outbound connections from the router to untrusted hosts following management interface activity
Detection Strategies
- Inspect HTTP traffic to the router management interface for oversized form parameters, particularly on /goform/* endpoints
- Deploy network intrusion detection signatures that flag POST requests exceeding expected parameter lengths to UTT firmware endpoints
- Correlate device crash logs with preceding HTTP requests to identify exploitation attempts
Monitoring Recommendations
- Forward router syslog and authentication events to a centralized log platform for retention and correlation
- Alert on access to the device administration interface from unexpected source IP addresses
- Track firmware version inventory to confirm exposure to the vulnerable build 3.1.1-190328 or earlier
How to Mitigate CVE-2025-6734
Immediate Actions Required
- Restrict access to the UTT HiPER 840G web management interface to trusted management VLANs only
- Block external WAN-side access to the device's HTTP/HTTPS administration ports at the perimeter
- Rotate any administrator credentials that may have been exposed to untrusted networks
- Audit device configuration for unauthorized changes to P2P traffic policies
Patch Information
No vendor patch is currently available. According to the disclosure, the vendor was contacted but did not respond. Organizations should monitor the VulDB advisory for any future firmware updates from UTT and consider replacing affected hardware with supported equipment if a fix is not released.
Workarounds
- Place the router management interface behind a VPN or jump host to eliminate direct network exposure
- Apply firewall rules limiting access to TCP ports used by the device web UI to a small allowlist of administrator IPs
- Disable remote administration on the WAN interface where the feature is not required
- Segment the affected device from sensitive internal networks until a vendor fix is published
# Example: restrict management interface access using upstream firewall rules
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -s <admin_subnet> -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -j DROP
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -s <admin_subnet> -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
