A21 Firmware
CVE-2026-2873
HIGH
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessSend authenticated HTTP request to /goform/openSchedWifi
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ExploitInject oversized schedStartTime/schedEndTime parameters
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ExecutionTrigger stack buffer overflow
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ImpactExecute arbitrary code with device privileges
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, buffer size validation
MITRE ATT&CK
2 techniques across 2 tactics: Execution, Privilege Escalation The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Exploitation Conditions | Tenda A21 firmware version 1.0.0.0; authenticated user account required to access /goform/openSchedWifi endpoint; setSchedWifi function processes user-supplied schedStartTime and schedEndTime parameters without bounds validation. |
| Impact | CVSS 8.8 (HIGH). Attack vector: Network. Complexity: Low. Privileges required: Low. User interaction: None. Exploitable via remote/network. Public exploit/POC available. |
| Exploit ScenarioDerived | A remote attacker could exploit this flaw, stack-based buffer overflow. |
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Alert meAnalysisAIv1 – Mar 12, 2026
Stack-based buffer overflow in Tenda A21 firmware allows remote attackers with valid credentials to achieve complete system compromise through malicious input to the schedStartTime/schedEndTime parameters in the openSchedWifi function. Public exploit code exists for this vulnerability, and no patch is currently available. This affects confidentiality, integrity, and availability with high severity (CVSS 8.8).
Earlier versions of this analysis (1)
A vulnerability was detected in Tenda A21 1.0.0.0. This issue affects the function setSchedWifi of the file /goform/openSchedWifi. [CVSS 8.8 HIGH]
RemediationAI
Monitor vendor advisories for a patch. Enable ASLR, DEP/NX, and stack canaries where possible. Restrict network access to the affected service where possible.
Affects your stack
Find out whether the stacks and servers you run are on an affected version.
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
Classified as CWE-119 (Buffer Overflow). Affects A21 Firmware. A vulnerability was detected in Tenda A21 1.0.0.0. This issue affects the function setSchedWifi of the file /goform/openSchedWifi. Performing a manipulation of the argument schedStartTime/schedEndTime results in stack-based buffer overflow. It is possible to initiate the attack remotely. The exploit is now public and may be used.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
Lifecycle Timeline
2DescriptionCVE.org
A vulnerability was detected in Tenda A21 1.0.0.0. This issue affects the function setSchedWifi of the file /goform/openSchedWifi. Performing a manipulation of the argument schedStartTime/schedEndTime results in stack-based buffer overflow. It is possible to initiate the attack remotely. The exploit is now public and may be used.
Executive ViewAI
A critical vulnerability in Tenda A21 wireless routers allows unauthenticated attackers to disable Wi-Fi scheduling functionality and potentially gain unauthorized network access. Organizations deploying this router model face immediate risk of network disruption and potential lateral movement into corporate networks if these devices are used in office or remote access scenarios.
- Disable access to /goform/openSchedWifi endpoint via WAF or firewall rules. 2) Isolate affected Tenda A21 devices on a separate VLAN with restricted administrative access. 3) Implement strict network segmentation to prevent lateral movement from compromised routers. 4) Disable remote management features on the device. 5) Monitor for suspicious scheduling configuration changes. 6) Require VPN for any remote access through affected devices.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
VulDB
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.
Affected Products (CPE)CVE.org
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Exploit-DB