CVE-2026-36784 Overview
CVE-2026-36784 is a stack 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 fromNetToolGet function, where the ip parameter is processed without proper bounds checking. Remote attackers can trigger the condition by sending a crafted HTTP request, causing a Denial of Service (DoS) on the affected device. The vulnerability is categorized under [CWE-121] Stack-based Buffer Overflow and requires no authentication or user interaction to exploit.
Critical Impact
Unauthenticated remote attackers can crash the Tenda O3 router and disrupt wireless network availability by sending a single malformed HTTP request to the fromNetToolGet endpoint.
Affected Products
- Shenzhen Tenda Technology Co., Ltd Tenda O3 Wireless Router
- Firmware version v1.0.0.5(4180)
- fromNetToolGet function handling the ip HTTP parameter
Discovery Timeline
- 2026-06-09 - CVE-2026-36784 published to NVD
- 2026-06-10 - Last updated in NVD database
Technical Details for CVE-2026-36784
Vulnerability Analysis
The Tenda O3 router exposes a web management interface that processes diagnostic requests through the fromNetToolGet function. This handler accepts an ip parameter supplied via HTTP and copies the value into a fixed-size stack buffer without validating its length. When an attacker submits an oversized ip value, the copy operation overruns the buffer boundary and corrupts adjacent stack memory, including the saved return address. The resulting memory corruption forces the HTTP daemon to crash, terminating the management interface and disrupting router operations. The attack is network-reachable and requires no credentials, making any exposed management interface a viable target.
Root Cause
The root cause is missing input length validation on the ip parameter inside the fromNetToolGet function. The function relies on unsafe string handling routines that do not enforce destination buffer limits, classifying the defect as a stack-based buffer overflow under [CWE-121]. Tenda's firmware shares this coding pattern across multiple parameters in the diagnostic endpoint family, which is a recurring issue in consumer-grade router firmware.
Attack Vector
Exploitation occurs over the network through a single HTTP request directed at the router's web management interface. The attacker supplies an excessively long string in the ip parameter of a request that reaches the vulnerable fromNetToolGet handler. Because the vulnerable parameter is parsed before any authentication check completes for this endpoint, the request triggers the overflow without valid credentials. The current public impact is limited to availability loss, though further analysis could reveal additional consequences if the corrupted stack data influences control flow. Proof-of-concept material is published in the referenced GitHub PoC Repository.
Detection Methods for CVE-2026-36784
Indicators of Compromise
- Unexpected reboots or service restarts of the Tenda O3 HTTP management daemon.
- HTTP requests targeting the diagnostic endpoint containing abnormally long ip query parameters.
- Loss of wireless connectivity correlated with inbound HTTP traffic to the router's management interface.
Detection Strategies
- Inspect web server and router logs for HTTP requests invoking fromNetToolGet with ip parameter values exceeding typical IPv4 string lengths.
- Deploy network IDS signatures that flag oversized parameters in HTTP requests destined for router management ports.
- Correlate router crash events with preceding HTTP traffic patterns to identify exploitation attempts.
Monitoring Recommendations
- Monitor availability of the router management interface and alert on repeated daemon restarts.
- Capture and review HTTP request payloads on management interfaces for anomalous parameter lengths.
- Track inbound connections to router administrative ports from untrusted networks.
How to Mitigate CVE-2026-36784
Immediate Actions Required
- Restrict access to the Tenda O3 web management interface to trusted internal hosts only.
- Disable remote (WAN-side) administration on the router until a vendor patch is available.
- Place vulnerable routers behind a firewall that filters unsolicited HTTP traffic to management ports.
Patch Information
No vendor patch or security advisory has been published for CVE-2026-36784 at the time of NVD release on 2026-06-09. Administrators should monitor Shenzhen Tenda Technology Co., Ltd communications for firmware updates that address the fromNetToolGet input validation defect. Until a fix is released, network-level mitigations are the only available defense.
Workarounds
- Segment vulnerable Tenda O3 routers onto isolated management VLANs with strict access control lists.
- Block inbound HTTP and HTTPS traffic to the router's management interface from all untrusted networks.
- Replace the affected device with a supported router model if patched firmware is not released within an acceptable timeframe.
- Apply rate limiting on the management interface to reduce the success rate of automated exploitation attempts.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
