CVE-2026-3815 Overview
CVE-2026-3815 is a buffer overflow vulnerability affecting UTT HiPER 810G routers running firmware versions up to 1.7.7-1711. The flaw resides in the strcpy function within the /goform/formApMail endpoint. Attackers can trigger the overflow remotely by sending crafted input to the affected web interface. The vulnerability is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer). Public exploit documentation is available, increasing the likelihood of opportunistic attacks against exposed devices.
Critical Impact
Remote attackers with low-level privileges can corrupt memory through the formApMail handler, potentially leading to arbitrary code execution or service disruption on the router.
Affected Products
- UTT HiPER 810G firmware versions up to 1.7.7-1711
- UTT HiPER 810G hardware revision 3.0
- UTT 810G firmware (all variants matching the vulnerable CPE)
Discovery Timeline
- 2026-03-09 - CVE-2026-3815 published to NVD
- 2026-03-10 - Last updated in NVD database
Technical Details for CVE-2026-3815
Vulnerability Analysis
The vulnerability stems from unsafe use of the strcpy C standard library function inside the handler for /goform/formApMail. The function copies attacker-controlled input into a fixed-size stack or heap buffer without validating the source length. When the input exceeds the destination capacity, adjacent memory is overwritten. On embedded MIPS or ARM-based routers like the UTT HiPER 810G, this corruption can overwrite saved return addresses or function pointers, enabling control-flow hijacking.
The /goform/formApMail endpoint is part of the device's web-based administration interface. An authenticated session with low privileges is required to reach the vulnerable code path, according to the CVSS vector. Successful exploitation impacts confidentiality, integrity, and availability of the device.
Root Cause
The root cause is the absence of bounds checking before strcpy copies user-supplied data into a finite buffer. The vulnerable function trusts the request payload size and does not enforce length limits or use safer alternatives such as strncpy or strlcpy. This pattern is common in legacy embedded firmware where defensive coding practices are inconsistent.
Attack Vector
An attacker sends an HTTP POST request to /goform/formApMail containing an oversized parameter that flows into the vulnerable strcpy call. Because the attack vector is network-based and complexity is low, exploitation can be automated against any reachable management interface. Public documentation of the issue is hosted on a GitHub Vulnerability Document and tracked in VulDB #349781. No verified proof-of-concept code is included here; refer to the linked references for technical details.
Detection Methods for CVE-2026-3815
Indicators of Compromise
- HTTP POST requests to /goform/formApMail with unusually long parameter values exceeding typical form field sizes.
- Unexpected reboots, watchdog resets, or crash logs from UTT HiPER 810G routers shortly after web interface activity.
- Outbound connections from the router to unfamiliar external hosts following administrative session activity.
Detection Strategies
- Inspect web server and access logs on the router for requests targeting formApMail with abnormal payload lengths.
- Deploy network intrusion detection signatures that flag oversized parameters in HTTP requests bound for UTT management endpoints.
- Correlate authentication events with subsequent requests to /goform/ paths to spot post-login exploitation attempts.
Monitoring Recommendations
- Forward router syslog output to a centralized logging platform and alert on crash or segmentation fault entries.
- Monitor management interface exposure using external scanning to confirm the web UI is not reachable from untrusted networks.
- Track firmware versions across the fleet and flag any device still running 1.7.7-1711 or earlier.
How to Mitigate CVE-2026-3815
Immediate Actions Required
- Restrict access to the router's web management interface to trusted administrative networks using ACLs or firewall rules.
- Rotate administrative credentials to limit the population of accounts that can reach the authenticated endpoint.
- Audit all UTT HiPER 810G devices in the environment and inventory their firmware versions.
Patch Information
No vendor advisory or patched firmware release has been published in the referenced sources at the time of NVD publication. Operators should monitor the VulDB entry #349781 and UTT vendor channels for updates. Until a fix is available, compensating controls are required.
Workarounds
- Disable the web administration interface on WAN-facing interfaces and limit it to a dedicated management VLAN.
- Place vulnerable devices behind a reverse proxy or WAF capable of enforcing maximum parameter lengths on /goform/ URIs.
- Replace end-of-life UTT HiPER 810G devices with supported hardware if a vendor patch is not forthcoming.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
