CVE-2026-0841 Overview
CVE-2026-0841 is a buffer overflow vulnerability in UTT 520W firmware version 1.7.7-180627. The flaw resides in the strcpy function call within the /goform/formPictureUrl handler. Attackers can manipulate the importpictureurl argument to overflow a fixed-size buffer. The vulnerability is exploitable remotely over the network and requires low privileges. The exploit code is publicly available, and the vendor was contacted before disclosure but did not respond. This issue is classified under CWE-119, covering improper restriction of operations within memory buffer bounds.
Critical Impact
Remote authenticated attackers can trigger a buffer overflow in the UTT 520W router web management interface, potentially leading to denial of service or arbitrary code execution on the embedded device.
Affected Products
- UTT 520W router (hardware revision 3.0)
- UTT 520W firmware version 1.7.7-180627
- Web management interface endpoint /goform/formPictureUrl
Discovery Timeline
- 2026-01-11 - CVE-2026-0841 published to the National Vulnerability Database
- 2026-01-13 - Last updated in NVD database
Technical Details for CVE-2026-0841
Vulnerability Analysis
The vulnerability exists in the web management firmware of the UTT 520W router. The HTTP handler bound to the /goform/formPictureUrl endpoint processes the importpictureurl parameter using the unsafe strcpy C library function. Because strcpy performs no bounds checking, an attacker-supplied string longer than the destination buffer overwrites adjacent stack memory.
The attack requires network reachability to the device management interface and low-level authentication. Successful exploitation impacts confidentiality, integrity, and availability of the device. Public proof-of-concept material is available in a GitHub PoC repository. Additional indexing is provided through VulDB #340441. The current EPSS probability is 0.189%.
Root Cause
The root cause is the use of strcpy without input validation on the importpictureurl parameter. Embedded MIPS or ARM-based router binaries that handle web form input through CGI-style formXXX handlers commonly suffer from this category of stack-based overflow [CWE-119]. The firmware does not enforce a maximum length on the supplied URL string before copying it into a fixed local buffer.
Attack Vector
An authenticated attacker sends a crafted HTTP request to /goform/formPictureUrl with an oversized importpictureurl value. The overflow corrupts the saved return address or adjacent stack data, enabling either a crash or controlled redirection of execution flow on the router. The vulnerability manifests entirely over the network without user interaction.
No verified exploitation code is published in this advisory beyond the referenced public proof-of-concept. Refer to the GitHub PoC Repository for technical details on the request structure.
Detection Methods for CVE-2026-0841
Indicators of Compromise
- HTTP POST requests to /goform/formPictureUrl containing abnormally long importpictureurl parameter values
- Unexpected reboots, watchdog resets, or crash logs on UTT 520W devices following inbound HTTP traffic
- Web management sessions originating from untrusted source addresses targeting the router administration interface
Detection Strategies
- Inspect HTTP traffic destined for router management interfaces and flag importpictureurl parameters exceeding expected length thresholds
- Deploy network intrusion detection signatures that match oversized POST bodies against /goform/formPictureUrl
- Correlate router availability loss with prior inbound HTTP requests to identify exploitation attempts
Monitoring Recommendations
- Forward router syslog and authentication events to a centralized log platform for anomaly review
- Monitor administrative access patterns to network edge devices for unauthorized authentication attempts
- Alert on repeated HTTP 5xx errors or connection resets from the router management service
How to Mitigate CVE-2026-0841
Immediate Actions Required
- Restrict access to the UTT 520W web management interface to trusted internal management VLANs only
- Disable remote WAN-side administration on affected devices until a firmware patch is released
- Rotate administrative credentials and enforce strong passwords to limit access available to low-privilege attackers
- Inventory all UTT 520W devices running firmware 1.7.7-180627 across the environment
Patch Information
No vendor patch is currently available. According to the disclosure, the vendor was contacted prior to public release but did not respond. Track the VulDB advisory entry for updates and contact UTT directly to request remediation guidance.
Workarounds
- Place affected routers behind an upstream firewall that filters inbound HTTP requests to the management interface
- Apply access control lists permitting management connections only from designated administrator hosts
- Consider replacing end-of-support UTT 520W devices with actively maintained network hardware where vendor patching is unreliable
# Example: restrict router management access using upstream firewall rules
# Replace with the management IP of your UTT 520W and trusted admin subnet
iptables -A FORWARD -p tcp -d 192.0.2.1 --dport 80 -s 10.0.0.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d 192.0.2.1 --dport 80 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
