A21 Firmware
CVE-2026-2870
HIGH
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessAuthenticate to Tenda A21 web interface
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ExploitSend crafted POST request to /goform/formSetQosBand
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ExecutionOverflow stack buffer in set_qosMib_list function
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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A06:2021 - Vulnerable and Outdated Components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 version 1.0.0.0 with web management interface enabled; requires valid login credentials to access /goform/formSetQosBand endpoint; QoS (Quality of Service) feature must be accessible through web administration panel. |
| 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
Remote code execution in Tenda A21 firmware through a stack buffer overflow in the QoS bandwidth configuration endpoint allows unauthenticated attackers to execute arbitrary code with full system privileges. Public exploit code exists for this vulnerability, and no patch is currently available. The flaw affects the set_qosMib_list function when processing unsanitized input, enabling network-based attacks from authenticated users or potentially lower-privileged roles.
Earlier versions of this analysis (1)
A security flaw has been discovered in Tenda A21 1.0.0.0. Affected by this issue is the function set_qosMib_list of the file /goform/formSetQosBand. [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 security flaw has been discovered in Tenda A21 1.0.0.0. Affected by this issue is the function set_qosMib_list of the file /goform/formSetQosBand. The manipulation of the argument list results in stack-based buffer overflow. The attack can be executed remotely. The exploit has been released to the public and may be used for attacks.
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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 security flaw has been discovered in Tenda A21 1.0.0.0. Affected by this issue is the function set_qosMib_list of the file /goform/formSetQosBand. The manipulation of the argument list results in stack-based buffer overflow. The attack can be executed remotely. The exploit has been released to the public and may be used for attacks.
Executive ViewAI
A high-severity vulnerability (CVSS 8.8) has been identified in Tenda A21 wireless routers affecting the QoS bandwidth management feature. Organizations using this device model face potential unauthorized access and network compromise, with public exploits already available. Since no vendor patch is currently available, immediate mitigation measures are required to protect network infrastructure.
Implement WAF rules to block POST requests to /goform/formSetQosBand; restrict administrative interface access via network ACLs to trusted IP ranges only; disable remote management on affected devices; segment affected routers on isolated VLANs; monitor for exploitation attempts; consider temporary device replacement if business-critical; enable all available device logging for forensic analysis.
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