CVE-2026-36783 Overview
CVE-2026-36783 is a stack-based buffer overflow vulnerability in the Shenzhen Tenda Technology Co., Ltd Tenda O3 Wireless Router firmware version v1.0.0.5(4180). The flaw resides in the domain parameter of the fromNetToolGet function. An unauthenticated attacker can submit a crafted HTTP request to overflow the stack buffer and cause a denial-of-service condition on the affected device. The vulnerability is classified under CWE-121: Stack-based Buffer Overflow and is exploitable remotely over the network without user interaction.
Critical Impact
Unauthenticated remote attackers can crash the Tenda O3 router by sending a single crafted HTTP request, disrupting network connectivity for all downstream clients.
Affected Products
- Shenzhen Tenda Technology Co., Ltd Tenda O3 Wireless Router
- Firmware version v1.0.0.5(4180)
- The fromNetToolGet function handling the domain HTTP parameter
Discovery Timeline
- 2026-06-09 - CVE-2026-36783 published to NVD
- 2026-06-10 - Last updated in NVD database
Technical Details for CVE-2026-36783
Vulnerability Analysis
The vulnerability resides in the fromNetToolGet function of the Tenda O3 router's web management interface. This function processes network diagnostic requests, including ping and traceroute operations submitted through the administrative HTTP endpoint. The domain parameter is copied into a fixed-size stack buffer without proper length validation. An attacker supplying an oversized value for this parameter overwrites adjacent stack memory, including saved return addresses and frame pointers. The resulting memory corruption causes the HTTP daemon to crash and renders the router unresponsive until it is rebooted.
Root Cause
The root cause is the absence of bounds checking on attacker-controlled input copied into a stack-allocated buffer. The fromNetToolGet handler trusts the length of the domain HTTP parameter and uses an unsafe string copy operation. This pattern is consistent with CWE-121: Stack-based Buffer Overflow and is common in embedded MIPS and ARM router firmware where compiler-level mitigations such as stack canaries and ASLR are often absent or incomplete.
Attack Vector
Exploitation requires network access to the router's web management interface. The attacker sends a single HTTP request to the vulnerable endpoint with an oversized domain parameter. No authentication or user interaction is required. The current public proof-of-concept targets denial of service, terminating the web service and disrupting router operation. Refer to the published GitHub PoC Repository for technical reproduction details.
Detection Methods for CVE-2026-36783
Indicators of Compromise
- Unexpected reboots or crashes of the Tenda O3 router web management service.
- HTTP POST or GET requests to endpoints invoking fromNetToolGet with abnormally long domain parameter values.
- Loss of management plane connectivity to the router while the data plane remains briefly active before failure.
Detection Strategies
- Inspect HTTP request logs at upstream proxies or firewalls for requests targeting the router's management interface with domain parameters exceeding typical hostname lengths.
- Deploy network intrusion detection signatures that flag oversized query parameters directed at the router's administrative URLs.
- Monitor for repeated TCP resets or connection failures to the router's HTTP management port following anomalous requests.
Monitoring Recommendations
- Restrict and log all access to the router's web administration interface from any source other than trusted management hosts.
- Capture and retain packet metadata for traffic destined to router management interfaces to support post-incident analysis.
- Alert on router availability changes through ICMP or SNMP probes to identify denial-of-service events quickly.
How to Mitigate CVE-2026-36783
Immediate Actions Required
- Block external access to the Tenda O3 web management interface from untrusted networks at the perimeter firewall.
- Disable remote management on the router if it is not strictly required for operations.
- Place affected devices on isolated management VLANs accessible only from authorized administrative hosts.
Patch Information
No vendor patch or security advisory from Shenzhen Tenda Technology Co., Ltd has been published for CVE-2026-36783 at the time of NVD publication. Administrators should monitor the Tenda official website for firmware updates addressing the fromNetToolGet stack overflow and apply them as soon as they become available.
Workarounds
- Limit HTTP access to the router's management interface using access control lists that allow only specific administrator IP addresses.
- Replace the affected device with a supported model if the vendor does not release a firmware update within an acceptable timeframe.
- Apply strict egress and ingress filtering to prevent untrusted hosts on the LAN from reaching the router's administrative endpoints.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
