CVE-2026-36770 Overview
CVE-2026-36770 is a stack-based buffer overflow vulnerability in Shenzhen Tenda Technology Co., Ltd Tenda US_W3V1.0BR firmware version v1.0.0.3. The flaw resides in the ask_to_reboot function, where the Go parameter is processed without proper bounds checking. Attackers can send crafted input over the network to trigger a stack overflow, resulting in a Denial of Service (DoS) condition. The vulnerability is classified under [CWE-121: Stack-based Buffer Overflow] and requires no authentication or user interaction to exploit.
Critical Impact
Remote attackers can trigger a Denial of Service against affected Tenda US_W3V1.0BR devices by submitting crafted input to the Go parameter, disrupting network availability for connected clients.
Affected Products
- Shenzhen Tenda Technology Co., Ltd Tenda US_W3V1.0BR
- Firmware version v1.0.0.3
- Devices exposing the ask_to_reboot function endpoint
Discovery Timeline
- 2026-06-09 - CVE-2026-36770 published to NVD
- 2026-06-09 - Last updated in NVD database
Technical Details for CVE-2026-36770
Vulnerability Analysis
The vulnerability exists in the ask_to_reboot function of the Tenda US_W3V1.0BR router firmware. The function fails to validate the length of the Go parameter before copying it into a fixed-size stack buffer. When an attacker submits an oversized value, the resulting overflow corrupts adjacent stack memory and crashes the responsible process. The attack vector is network-based, requires no privileges, and demands no user interaction.
Exploitation produces a Denial of Service rather than code execution, based on the CVSS impact profile that scores availability impact as high while confidentiality and integrity remain unaffected. The EPSS score of 0.04% reflects low observed exploitation activity at this time. A proof-of-concept is publicly available in the GitHub PoC Repository.
Root Cause
The root cause is missing input length validation on the Go HTTP request parameter before it is copied into a stack-allocated buffer inside the ask_to_reboot handler. This is a classic [CWE-121] stack-based buffer overflow caused by unsafe string handling in the embedded web management interface.
Attack Vector
An unauthenticated remote attacker reachable over the network sends a specially crafted HTTP request containing an oversized Go parameter value to the router's management interface. The malformed request reaches the ask_to_reboot function, overflows the stack buffer, and crashes the service. Repeated requests can sustain the DoS condition, keeping the device unavailable until reboot or recovery.
No verified exploit code is reproduced here. Technical details and a proof-of-concept are documented in the GitHub PoC Repository.
Detection Methods for CVE-2026-36770
Indicators of Compromise
- HTTP requests to the router management interface containing abnormally long values in the Go parameter targeting the ask_to_reboot endpoint.
- Unexpected reboots, crashes, or service restarts of the Tenda US_W3V1.0BR web management daemon.
- Loss of management plane availability while the WAN/LAN data plane remains partially responsive.
Detection Strategies
- Inspect inbound HTTP traffic to router management interfaces for oversized parameter values, especially Go, using network intrusion detection signatures.
- Correlate router availability metrics with HTTP request logs to identify crash patterns aligned with malformed ask_to_reboot requests.
- Monitor SNMP or syslog feeds from affected devices for repeated service restarts of the web management process.
Monitoring Recommendations
- Forward router syslog and management plane logs to a centralized log platform for parameter-length and crash analysis.
- Alert on multiple management-interface restarts within a short interval on the same device.
- Track external network traffic targeting the router's HTTP/HTTPS management ports from untrusted sources.
How to Mitigate CVE-2026-36770
Immediate Actions Required
- Restrict access to the router's management interface to trusted internal networks only and block exposure to the public internet.
- Disable remote management features on Tenda US_W3V1.0BR devices if they are not strictly required for operations.
- Monitor the vendor's support channels for a firmware update addressing the ask_to_reboot stack overflow.
Patch Information
At the time of publication, no vendor patch is referenced in the NVD entry for CVE-2026-36770. Administrators should track Shenzhen Tenda Technology Co., Ltd advisories for an updated firmware release that fixes input validation in the ask_to_reboot function. Until a patch is available, apply network-level mitigations to limit exposure.
Workarounds
- Place affected routers behind a firewall that filters inbound HTTP requests with abnormally long parameter values.
- Apply ACLs to permit management-interface access only from designated administrator IP addresses.
- Segment vulnerable devices onto isolated VLANs to limit the blast radius of a successful DoS.
- Consider replacing end-of-life or unsupported Tenda hardware with currently maintained models if no patch is forthcoming.
# Example: restrict router management interface access with iptables on an upstream gateway
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.
