CVE-2025-71021VulnerabilityPublished 14 Jan 2026

CVE-2025-71021: n/a

Source CVE Database V5

Not known to be exploited · CVSS 7.5 High.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 39% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, 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: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; 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 impacted component (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).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 14 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
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), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC 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

AI-suggested

1. Monitor Tenda’s official channels for firmware updates addressing CVE-2025-71021 and apply patches promptly once released. 2. Restrict access to router management interfaces by implementing network segmentation and firewall rules to limit exposure to trusted IP addresses only. 3. Disable remote management features if not required to reduce the attack surface. 4. Employ intrusion detection/prevention systems (IDS/IPS) to detect anomalous or malformed requests targeting the serverName parameter or unusual traffic patterns to the router. 5. Conduct regular network device audits to inventory and identify vulnerable Tenda AX-1806 devices within the environment. 6. Consider replacing vulnerable routers with models from vendors with stronger security track records if patching is delayed or unavailable. 7. Educate IT staff on recognizing signs of DoS attacks and establishing incident response procedures to quickly isolate affected devices. 8. Implement network-level rate limiting to mitigate the impact of potential flooding attacks exploiting this vulnerability.

Description

CVE-2025-71021 is a high-severity stack overflow vulnerability found in the Tenda AX-1806 router firmware version 1.0.0.1. The flaw exists in the handling of the serverName parameter within the sub_65A28 function, allowing remote attackers to trigger a Denial of Service (DoS) by sending a crafted request. This vulnerability requires no authentication or user interaction and can be exploited over the network. Although no known exploits are currently in the wild, the vulnerability's CVSS score of 7.5 indicates a significant risk to availability. European organizations using this router model could face network disruptions if targeted. Mitigation includes applying vendor patches once available, restricting access to router management interfaces, and monitoring network traffic for anomalous requests targeting the serverName parameter.

Impact

For European organizations, the primary impact of CVE-2025-71021 is the potential for network outages caused by Denial of Service attacks targeting Tenda AX-1806 routers. This can disrupt internet connectivity, internal communications, and access to critical online services. Organizations relying on these routers for perimeter or internal network routing may experience downtime affecting operational continuity. The lack of confidentiality or integrity impact reduces risks related to data breaches but does not diminish the operational risks. Critical infrastructure sectors such as finance, healthcare, and government agencies could face significant disruptions if their networks use vulnerable devices. Additionally, small and medium enterprises (SMEs) that deploy consumer-grade or low-cost networking equipment like Tenda routers may be particularly exposed. The absence of known exploits in the wild currently limits immediate threat but does not preclude future exploitation, especially as proof-of-concept code or automated scanning tools emerge. The vulnerability's ease of exploitation without authentication increases the likelihood of opportunistic attacks, especially in environments with exposed management interfaces or weak network segmentation.

Summary

CVE-2025-71021 identifies a stack overflow vulnerability in the Tenda AX-1806 router firmware version 1.0.0.1, specifically within the sub_65A28 function's processing of the serverName parameter. A stack overflow occurs when more data is written to a buffer located on the stack than it can hold, potentially overwriting adjacent memory and causing unpredictable behavior. In this case, the crafted request exploits improper bounds checking on the serverName input, leading to a crash of the router’s service and resulting in Denial of Service (DoS). The vulnerability is remotely exploitable without requiring authentication or user interaction, increasing its risk profile. The CVSS v3.1 base score of 7.5 reflects a high severity due to the network attack vector, low attack complexity, and the impact limited to availability (no confidentiality or integrity impact). No patches or exploits are currently publicly available, but the vulnerability is published and reserved as of early 2026. The CWE-121 classification highlights that the root cause is a classic stack-based buffer overflow, a common and well-understood software flaw. This vulnerability could be leveraged by attackers to disrupt network connectivity and services dependent on the affected router, potentially impacting business continuity.

CWE-121Stack-based Buffer Overflow (opens in a new tab)
Variant weaknessLikelihood of exploit: HighCWE Top 25 (2025): #14
A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).
Operation · Build and Compilation · Environment Hardening
Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index…
Architecture and Design
Use an abstraction library to abstract away risky APIs. Not a complete solution.
Implementation
Implement and perform bounds checking on input.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

github.com/0-fool/VulnbyCola/blob/main/Tenda/AX-1806/7/1.md (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 21 Jan 2026, 20:42 UTC

WeaknessesCWE-121

Technical details

References

Community reviews

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