Tenda O3v3
CVE-2026-36791
HIGH
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessReach device HTTP interface over network
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DeliverySend crafted POST to formSetCfm
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ExploitOversized save_list_data overflows stack buffer
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Executionhttpd process crashes or device reboots
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ImpactCPE availability lost for users
Vulnerability Assessment
| Weakness |
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Stack buffer bounds checking
MITRE ATT&CK
1 technique across 1 tactic: Execution The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Exploitation Conditions | The attacker needs network reachability to the Tenda O3v3's HTTP management interface on a device running firmware v1.0.0.5, and must be able to issue a POST request to the formSetCfm endpoint with an attacker-controlled save_list_data parameter. No authentication, no user interaction, and no non-default configuration are required per the CVSS vector (PR:N/UI:N/AC:L). Exploitation is meaningfully limited where the management interface is bound only to the LAN side or restricted by ACL, and to the specific O3v3 hardware running this exact firmware build - other Tenda models or firmware revisions are not in scope of this CVE. |
| Impact | The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) reflects network-reachable, unauthenticated, low-complexity exploitation with availability-only impact - consistent with a DoS-only stack overflow. EPSS is extremely low at 0.01% (2nd percentile) and the issue is not on the CISA KEV list, indicating no observed mass exploitation. The reported finding originates from an LLM-assisted vulnerability research project (SemVulLLM) rather than a vendor advisory or in-the-wild incident, which lowers urgency but does not eliminate it. Real-world risk is concentrated to organizations exposing the Tenda O3v3 management interface to untrusted networks; on properly segmented LAN-only management, residual risk is low. Note also a signal conflict worth flagging: although CWE-121 stack overflows often enable code execution, this CVE's impact metrics explicitly limit it to availability, so RCE should not be assumed without independent verification. |
| Exploit ScenarioDerived | An attacker with network reachability to the Tenda O3v3's web management interface sends a single crafted HTTP POST to the endpoint backed by formSetCfm with an oversized save_list_data value, overflowing a stack buffer and crashing the httpd process or rebooting the device. Repeating the request keeps the CPE offline, disrupting the wireless link or backhaul it provides. No public exploit identified at time of analysis, but the bug is simple enough that a PoC can be derived directly from the referenced research repository. |
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Alert meAnalysisAIv1 – Jun 10, 2026
Denial of service in Tenda O3v3 firmware v1.0.0.5 allows remote unauthenticated attackers to crash the device by sending a crafted HTTP request that triggers a stack buffer overflow in the formSetCfm handler. No public exploit identified at time of analysis, and EPSS is very low (0.01%), but the network-reachable, no-authentication attack surface on a CPE/router device makes this relevant for exposed deployments.
RemediationAI
No vendor-released patch identified at time of analysis. Operators of Tenda O3v3 v1.0.0.5 should check Tenda's support portal for a firmware update addressing formSetCfm and apply it once available, and in the interim restrict access to the device's HTTP management interface to a trusted management VLAN or specific administrator IPs via ACL - this eliminates remote exploitability but means administrators must use a jump host or on-site access for configuration. Disabling remote/WAN-side web administration if enabled is a high-value compensating control with minimal operational impact for most deployments. As a last resort where exposure cannot be reduced, monitor for unexpected device reboots and place the device behind an upstream firewall that can rate-limit or filter unusual POST requests to the form handlers; this will not prevent a determined attacker on the same network segment. Research reference for triage: https://github.com/xhh0124/SemVulLLM/tree/main/O3/formSetCfm.
Affects your stack
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Technical ContextAI · show details
The Tenda O3v3 is an outdoor CPE/wireless bridge product. The vulnerable component is the web management interface's formSetCfm handler, which processes the save_list_data parameter without sufficient bounds checking before copying it onto the stack. This is a classic CWE-121 stack-based buffer overflow in embedded MIPS/ARM router firmware - the same vulnerability class that has affected numerous Tenda HTTP handlers historically, typically caused by use of unsafe string functions (strcpy/sprintf) on attacker-controlled HTTP form fields. CPE data is not meaningfully populated by NVD (placeholder n/a:n/a), so the affected target must be derived from the description rather than structured CPE matching.
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Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Primary rating from Vendor (mitre) · only source for this CVE.
CVSS VectorVendor: mitre
Lifecycle Timeline
2DescriptionCVE.org
Shenzhen Tenda Technology Co., Ltd Tenda O3v3 v1.0.0.5 was discovered to contain a stack overflow in the save_list_data parameter of the formSetCfm function. This vulnerability allows attackers to cause a Denial of Service (DoS) via a crafted HTTP request.
Executive ViewAI
Tenda O3v3 router firmware v1.0.0.5 contains a remotely exploitable denial-of-service vulnerability that allows unauthenticated attackers to crash the device, potentially disrupting network connectivity for all downstream users. Organizations deploying this model should immediately identify affected devices and assess their criticality to business operations, as the network-reachable attack surface requires no authentication and presents clear availability risk.
Segment the affected device from untrusted networks using firewall rules or VLAN isolation; disable HTTP management interface if not actively used; implement network-based rate limiting or intrusion detection signatures for suspicious HTTP traffic patterns; monitor device uptime and reboot events for anomalies; maintain backup connectivity or redundant devices if this router is critical to operations.
Threat Intelligence Overview
NVD
CVE.org
EPSS
Vulnrichment
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.
A stack-based buffer overflow occurs when a program writes more data to a buffer located on the stack than it was allocated to hold.
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.
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