CVE-2026-1140 Overview
CVE-2026-1140 is a buffer overflow vulnerability in UTT 进取 520W router firmware version 1.7.7-180627. The flaw resides in the strcpy function call within the /goform/ConfigExceptAli endpoint. Attackers can manipulate input to trigger memory corruption remotely over the network. The exploit has been disclosed publicly, increasing the risk of opportunistic attacks against exposed devices. UTT was contacted prior to disclosure but did not respond, leaving affected devices without official remediation guidance. The vulnerability is categorized under [CWE-119] for improper restriction of operations within the bounds of a memory buffer.
Critical Impact
Remote attackers with low-privileged access can trigger a buffer overflow in the UTT 520W web management interface, potentially leading to arbitrary code execution or device compromise.
Affected Products
- UTT 520W router hardware (version 3.0)
- UTT 520W firmware version 1.7.7-180627
- Deployments exposing the /goform/ConfigExceptAli endpoint
Discovery Timeline
- 2026-01-19 - CVE-2026-1140 published to NVD
- 2026-02-04 - Last updated in NVD database
Technical Details for CVE-2026-1140
Vulnerability Analysis
The vulnerability exists in the request handler for /goform/ConfigExceptAli within the UTT 520W web management interface. The handler invokes strcpy to copy user-supplied data into a fixed-size stack buffer without performing length validation. Sending an oversized string overflows the destination buffer and corrupts adjacent stack memory, including saved return addresses. Successful exploitation can cause service disruption or allow execution of attacker-controlled code in the context of the web server process. The vendor confirmed no response to disclosure attempts, so no official patch is currently available.
Root Cause
The root cause is unsafe use of the strcpy C library function, which does not enforce destination buffer boundaries. The ConfigExceptAli form handler trusts attacker-controlled input from HTTP requests and copies it directly into a stack-allocated buffer. This pattern aligns with [CWE-119], improper restriction of operations within the bounds of a memory buffer. Embedded router firmware frequently relies on legacy string handling functions, which makes this class of flaw common in consumer and small-business networking equipment.
Attack Vector
An authenticated attacker with low-privileged credentials can reach the vulnerable endpoint over the network. The attack does not require user interaction and has low complexity. A crafted HTTP request containing an overlong parameter value to /goform/ConfigExceptAli triggers the overflow. Public disclosure of exploit details on third-party platforms increases the likelihood of automated scanning and weaponization against internet-facing UTT 520W devices.
The vulnerability manifests when the form handler copies request parameter data into a fixed-size stack buffer using strcpy. See the GitHub CVE Overview and VulDB #341731 for technical details on the affected code path.
Detection Methods for CVE-2026-1140
Indicators of Compromise
- HTTP POST requests to /goform/ConfigExceptAli containing unusually long parameter values
- Unexpected reboots, web service crashes, or watchdog resets on UTT 520W devices
- Outbound connections from the router to unknown external hosts following management interface access
- Authentication events from unfamiliar source IPs on the router admin portal
Detection Strategies
- Inspect web server access logs on the device for requests targeting /goform/ConfigExceptAli with abnormal payload sizes
- Deploy network intrusion detection signatures that flag oversized POST bodies destined for UTT management endpoints
- Correlate router crash events with prior HTTP requests to the vulnerable form handler
Monitoring Recommendations
- Restrict and monitor administrative access to the router web interface from trusted management networks only
- Forward router system and authentication logs to a centralized log platform for anomaly review
- Track firmware version inventory to identify devices still running the affected build 1.7.7-180627
How to Mitigate CVE-2026-1140
Immediate Actions Required
- Remove UTT 520W devices from internet-facing exposure and restrict the web management interface to internal management VLANs
- Rotate all administrative credentials on affected devices to limit reuse by low-privileged attackers
- Audit access control lists to ensure only trusted hosts can reach /goform/ConfigExceptAli
- Evaluate replacement with a supported router platform given the vendor's lack of response to disclosure
Patch Information
No vendor patch is available. UTT did not respond to disclosure attempts, and no fixed firmware version has been published. Operators should treat the affected firmware as unsupported and plan compensating controls or hardware replacement. Monitor the VulDB advisory and GitHub CVE Overview for any future updates.
Workarounds
- Block external access to the router HTTP/HTTPS management ports at the perimeter firewall
- Disable remote web administration features where configuration allows
- Place the router behind a network segmentation boundary that restricts access to authenticated administrators only
- Implement upstream web application firewall rules to drop requests with oversized parameters targeting /goform/ paths
# Example perimeter firewall rule to block external access to router management
iptables -A INPUT -p tcp --dport 80 -i wan0 -j DROP
iptables -A INPUT -p tcp --dport 443 -i wan0 -j DROP
# Allow management access only from trusted internal subnet
iptables -A INPUT -p tcp -s 10.0.10.0/24 --dport 80 -j ACCEPT
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
