Tenda O3 Router
CVE-2026-36779
HIGH
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessIdentify exposed Tenda O3 web UI
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DeliverySend crafted HTTP request to fromVirtualSer
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ExploitOverflow stack buffer in parameter handler
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ExecutionCrash httpd / reboot router
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ImpactSustained denial of service
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 | Attacker requires network reachability to the Tenda O3's HTTP management interface (port 80/443 on the router) and the ability to send a crafted HTTP request to the fromVirtualSer handler - no credentials, no user interaction, and no non-default configuration are required per the CVSS vector (AV:N/AC:L/PR:N/UI:N). Exploitation is LIMITED to the specific firmware version v1.0.0.5(4180); deployments where the web UI is bound only to the LAN/WLAN interface (the typical default) restrict attackers to local network adjacency, while exposure widens dramatically if WAN-side remote management has been enabled. Impact is limited to denial of service per the CVSS scope (C:N/I:N/A:H); code execution is not confirmed by the available data despite the stack-overflow primitive. |
| Impact | The CVSS 7.5 (AV:N/AC:L/PR:N/UI:N/C:N/I:N/A:H) reflects a pure availability impact reachable by an unauthenticated network attacker with low complexity - consistent with a remote DoS against an embedded HTTP service. However, EPSS at 0.01% (2nd percentile) and absence from CISA KEV indicate negligible observed or predicted in-the-wild exploitation. The CWE-121 classification combined with five overlapping stack overflow sinks raises a latent concern that the same primitive could be escalated to code execution on this MIPS/ARM-class device, but the CVSS vector explicitly scopes impact to availability only (C:N/I:N) - defenders should treat the published RCE potential as unconfirmed. A key caveat: the CVSS vector assumes the management interface is network-reachable; many deployments expose it only on the LAN/WLAN side, which materially reduces real-world exposure unless WAN-side management is enabled. |
| Exploit ScenarioDerived | An attacker on the same network segment as the router - or on the internet if WAN-side management is enabled - sends a single crafted HTTP POST to the fromVirtualSer endpoint containing an oversized value in one of the vulnerable parameters. The router's httpd process crashes, dropping the management UI and potentially knocking the device into a reboot loop, severing connectivity for all clients behind it. No authentication and no user interaction are required, and the attack can be trivially scripted against many devices. |
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Alert meAnalysisAIv1 – Jun 10, 2026
Denial of service in Tenda O3 Wireless Router firmware v1.0.0.5(4180) allows remote unauthenticated attackers to crash the device by sending crafted HTTP requests that trigger stack buffer overflows in the fromVirtualSer function. Five distinct overflow sinks (puVar2, puVar1, __s2, __s1_00, puVar3) are reachable via the same handler. No public exploit identified at time of analysis, and EPSS rates exploitation likelihood at 0.01%, but a research repository with vulnerability artifacts is referenced.
RemediationAI
No vendor-released patch identified at time of analysis - the only reference is a third-party GitHub research repository (https://github.com/xhh0124/SemVulLLM/tree/main/O3/fromVirtualSer), not a Tenda advisory. Until Tenda publishes updated firmware for the O3, restrict access to the device's web management interface by disabling remote/WAN-side administration (this prevents internet-borne exploitation but does not block LAN/WLAN attackers and may inconvenience admins managing remote sites), placing the management VLAN behind an ACL that only permits trusted administrative hosts, and blocking inbound HTTP/HTTPS to the router's WAN IP at any upstream firewall. Monitor Tenda's support portal for firmware later than v1.0.0.5(4180) and apply it once released; given Tenda's history with SOHO router vulnerabilities, consider replacing end-of-life O3 units with actively maintained hardware if no patch materializes.
Affects your stack
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Technical ContextAI · show details
The Tenda O3 is a SOHO/outdoor wireless router whose web-based management interface exposes a CGI-style handler named fromVirtualSer, typically responsible for processing virtual server (port-forwarding) configuration submissions. The flaw is classified as CWE-121 (Stack-based Buffer Overflow), meaning user-supplied HTTP parameters are copied into fixed-size stack buffers without adequate length validation - likely via unbounded strcpy/sprintf-style operations on the listed variables. On embedded MIPS/ARM routers running stripped-down Linux without modern stack protections (canaries, ASLR, NX often partial), such overflows reliably corrupt the saved return address and crash the httpd daemon. The CPE entry is generic ('n/a'), so authoritative product enumeration must come from the description rather than NVD 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 O3 Wireless Router v1.0.0.5(4180) was discovered to contain multiple stack overflows in the fromVirtualSer function via the puVar2, puVar1, __s2, __s1_00, and puVar3 parameters. These vulnerabilities allow attackers to cause a Denial of Service (DoS) via a crafted HTTP request.
Executive ViewAI
Tenda O3 wireless routers running affected firmware versions are exposed to unauthenticated remote denial-of-service attacks that crash devices, potentially disrupting network operations across impacted sites. No vendor patch is available, leaving deployed units at persistent risk. Organizations must immediately identify affected devices and implement interim protections to maintain network availability pending vendor remediation.
Restrict management HTTP access via firewall rules and network segmentation; implement rate-limiting on HTTP requests to affected routers; disable remote management features where operationally feasible; establish HTTP traffic logging to detect exploitation attempts; maintain continuous monitoring of vendor advisory channels for patch releases.
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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