VulnerabilityPublished 21 Feb 2026Updated 23 Feb 2026

CVE-2026-2886: Tenda A21 · Stack-based Buffer Overflow

Affects Tenda A21Source CVE Database V5

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Public exploit available · CVSS 8.7 High.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 4.0 base score

8.7High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.6% chance of exploitation in 30 days – higher than 50% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P

Base metrics

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
Vulnerable system confidentiality: High
Vulnerable system integrity: High
Vulnerable system availability: High
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Threat metrics

Exploit Maturity: POC

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: High: There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Vulnerable system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Vulnerable System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
Exploit Maturity: POC: Based on threat intelligence sources each of the following must apply: · Proof-of-concept is publicly available · No knowledge of reported attempts to exploit this vulnerability · No knowledge of publicly available solutions used to simplify attempts to exploit the vulnerability

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 21 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
CVSS exploit maturity: proof of concept public
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CVSS vector, the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
TendaA21	Affected =1.0.0.0	Fixed in–

AI-suggested

To mitigate CVE-2026-2886, organizations should immediately check for and apply any official firmware updates or patches released by Tenda addressing this vulnerability. In the absence of patches, network administrators should restrict access to the router's management interfaces by implementing network segmentation and firewall rules that limit exposure to trusted IP addresses only. Disabling remote management features and changing default credentials can reduce attack surface. Monitoring network traffic for unusual activity targeting the /goform/SetOnlineDevName endpoint may help detect exploitation attempts. Employing intrusion detection/prevention systems (IDS/IPS) with signatures for this vulnerability can provide additional protection. Organizations should also consider replacing affected devices with models from vendors with more robust security support if timely patches are unavailable. Regular security audits and vulnerability assessments of network infrastructure are recommended to identify and remediate similar risks proactively.

Description

A weakness has been identified in Tenda A21 1.0.0.0. This affects the function set_device_name of the file /goform/SetOnlineDevName. This manipulation of the argument devName causes stack-based buffer overflow. It is possible to initiate the attack remotely. The exploit has been made available to the public and could be used for attacks.

Impact

The impact of CVE-2026-2886 is substantial for organizations using Tenda A21 routers. Successful exploitation can lead to full compromise of the device, allowing attackers to execute arbitrary code remotely. This can result in unauthorized access to internal networks, interception or manipulation of sensitive data, disruption of network services, and potential lateral movement to other critical systems. The vulnerability threatens confidentiality by exposing network traffic and device configurations, integrity by allowing malicious modifications, and availability by potentially causing device crashes or denial of service. Given the router's role as a network gateway, exploitation could undermine the security posture of entire organizational networks, affecting business continuity and data protection obligations. The public availability of exploit code increases the likelihood of attacks, especially targeting unpatched or poorly managed devices.

Summary

CVE-2026-2886 identifies a critical stack-based buffer overflow vulnerability in the Tenda A21 router firmware version 1.0.0.0. The vulnerability resides in the set_device_name function, specifically in the /goform/SetOnlineDevName endpoint, which processes the devName parameter. Due to insufficient bounds checking on this input, an attacker can supply a crafted devName string that overflows the stack buffer, overwriting adjacent memory. This overflow can be exploited remotely without requiring authentication or user interaction, enabling an attacker to execute arbitrary code with the privileges of the affected process. The vulnerability has a CVSS 4.0 base score of 8.7, reflecting its high impact on confidentiality, integrity, and availability. The exploit has been publicly disclosed, increasing the risk of exploitation, although no active exploitation in the wild has been confirmed to date. The lack of available patches or official mitigations from the vendor at the time of disclosure further elevates the threat. This vulnerability could allow attackers to gain control over the router, intercept or manipulate network traffic, or pivot into internal networks, posing significant risks to organizational security.

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What to do

Affected software

Description

AI analysisMachine-generated, updated 1 Mar 2026, 06:15 UTC

Technical details

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