CVE-2026-5566: UTT HiPER 1250GW Buffer Overflow Flaw

CVE-2026-5566 Overview

CVE-2026-5566 is a buffer overflow vulnerability in the UTT HiPER 1250GW router, affecting firmware versions up to 3.2.7-210907-180535. The flaw resides in the strcpy call within the /goform/formNatStaticMap handler. An attacker can manipulate the NatBind argument to overflow a fixed-size buffer. The exploit is publicly disclosed and can be triggered remotely against authenticated sessions. The weakness is categorized under CWE-119, improper restriction of operations within the bounds of a memory buffer.

Critical Impact
Remote attackers with low-privilege access can corrupt router memory through the NatBind parameter, potentially achieving arbitrary code execution on the device and full compromise of the network gateway.

Affected Products

UTT HiPER 1250GW router firmware versions up to 3.2.7-210907-180535
Web management interface endpoint /goform/formNatStaticMap
NAT static mapping configuration component processing the NatBind argument

Discovery Timeline

2026-04-05 - CVE-2026-5566 published to NVD
2026-04-24 - Last updated in NVD database

Technical Details for CVE-2026-5566

Vulnerability Analysis

The vulnerability lies in the HTTP request handler responsible for NAT static mapping configuration on the UTT HiPER 1250GW. The handler is reachable through the /goform/formNatStaticMap URI on the device's web management interface. When the handler parses the NatBind POST parameter, it copies the attacker-controlled string into a fixed-size stack buffer using strcpy without validating the source length. Because strcpy terminates only on a null byte, supplying an overly long NatBind value writes past the buffer boundary and corrupts adjacent stack memory, including saved return addresses on MIPS-based embedded targets. Successful exploitation can crash the httpd service or redirect execution to attacker-supplied payloads, granting control of the device.

Root Cause

The root cause is unsafe use of the strcpy function on attacker-controlled input. The web handler does not enforce a maximum length on the NatBind parameter before copying it into a local buffer. This pattern reflects [CWE-119], where the program performs operations on a memory buffer without bounds validation. Embedded routers frequently lack stack canaries, ASLR, and non-executable stacks, which increases the reliability of overflow exploitation.

Attack Vector

Exploitation requires network access to the device's management interface and low-privilege authentication. An attacker sends a crafted HTTP POST request to /goform/formNatStaticMap containing an overlong NatBind value. The malicious request causes the strcpy operation to overwrite stack memory, leading to denial of service or arbitrary code execution within the httpd process context. Public proof-of-concept material referenced in the GitHub CVE Issue Discussion and VulDB Vulnerability Detail #355336 describes the trigger conditions.

No verified exploitation code is included here. Refer to the linked advisories for technical reproduction details.

Detection Methods for CVE-2026-5566

Indicators of Compromise

HTTP POST requests to /goform/formNatStaticMap containing unusually long NatBind parameter values, particularly above 256 bytes.
Unexpected restarts or crashes of the httpd process on UTT HiPER 1250GW devices, visible as gaps in management session availability.
New or modified NAT static mapping entries on the router that were not authorized by administrators.

Detection Strategies

Inspect web access logs on the router and upstream proxies for requests targeting /goform/formNatStaticMap with oversized POST bodies or non-ASCII payloads in NatBind.
Deploy network IDS signatures that flag POST requests to UTT /goform/ endpoints exceeding expected parameter lengths.
Correlate authentication events with NAT configuration changes to identify abuse of low-privilege accounts.

Monitoring Recommendations

Forward router syslog and management interface logs to a centralized SIEM and alert on repeated httpd crashes or watchdog reboots.
Monitor outbound connections originating from the router itself, which is atypical and may indicate post-exploitation command-and-control activity.
Track administrative logins from unexpected source IP ranges, especially from the WAN side if remote management is enabled.

How to Mitigate CVE-2026-5566

Immediate Actions Required

Restrict access to the router's web management interface to trusted management VLANs and disable WAN-side administration.
Rotate all administrative and low-privilege credentials on affected UTT HiPER 1250GW devices to limit authenticated attack paths.
Audit existing NAT static mapping entries for unauthorized changes and remove any unknown rules.

Patch Information

No vendor patch is referenced in the available advisory data. Operators should contact UTT for firmware updates addressing the formNatStaticMap handler and monitor the VulDB Vulnerability Detail #355336 entry for updates. Until a fix is available, treat affected devices as exposed and apply network-layer controls.

Workarounds

Place the router management interface behind a firewall ACL that allows access only from a dedicated administrative subnet.
Disable remote (WAN) management entirely if business operations do not require it.
Where feasible, replace end-of-support UTT HiPER 1250GW units with vendor-supported hardware that receives active security updates.

bash

# Example firewall ACL to restrict management access to a trusted 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
iptables -A INPUT -p tcp --dport 443 -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP