What is the CVSS score of CVE-2025-7421?

CVE-2025-7421 has a CVSS 3.1 base score of 8.8 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.4%.

Is there a public PoC exploit available for CVE-2025-7421?

Yes, a public proof-of-concept exploit is available for CVE-2025-7421. Prioritise patching immediately. EPSS: 0.4%.

How to fix or mitigate CVE-2025-7421?

Within 24 hours: Identify and inventory all Tenda O3V2 1.0.0.12(3880) devices in your environment; isolate affected devices from critical systems if possible. Within 7 days: Implement network segmentation to restrict access to the vulnerable httpd service; deploy WAF rules to block malicious MAC filter requests if internet-exposed; monitor for exploitation attempts. Within 30 days: Replace vulnerable Tenda devices with patched/alternative vendors; if replacement unavailable, maintain strict network access controls and continuous monitoring until vendor patch is released.

O3 Firmware CVE-2025-7421

EUVD-2025-21090 HIGH

Buffer Overflow (CWE-119)

2025-07-11 cna@vuldb.com

Buffer Overflow Tenda O3 Firmware

8.8

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-119 OWASP Top 10:2025 A06:2021 - Vulnerable and Outdated Components ASVS 5.0 V15 - Secure Coding and Architecture Bounds checking, buffer size validation MITRE ATT&CK 2 techniques across 2 tactics: Execution,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. Sign in to read
Impact	This vulnerability represents a HIGH real-world risk despite the authentication requirement. CVSS 8.8 reflects the severity accurately: AV:N (network-accessible), AC:L (low complexity exploitation), PR:L (low privilege - requires authenticated user), UI:N (no user interaction), and full impact across C/I/A. The critical risk factors are: (1) Public exploit disclosure significantly reduces time-to-weaponization; (2) Stack-based buffer overflows are reliably exploitable with high success rates; (3) The httpd service is typically accessible to LAN-connected devices or compromised sessions; (4) No mention of ASLR/DEP in typical router firmware reduces exploitation complexity; (5) The device controls network access, making RCE impact severe. Conversely, the PR:L requirement provides some friction - an attacker needs valid credentials or session access. EPSS scoring would likely be elevated (0.75+) due to public POC availability. This should be treated as an urgent patch priority for deployed systems.
Exploit ScenarioDerived	A user connected to the target router's network (or with compromised LAN access) authenticates to the router's web interface. The attacker sends a crafted POST request to /goform/operateMacFilter with an oversized 'mac' parameter containing a malicious payload (typically shellcode). The payload overflows the stack buffer in fromMacFilterModify, overwrites the return address, and redirects execution to the attacker's code. Given the low AC:L rating and public POC availability, this exploitation is reliable and requires minimal sophistication. The attacker gains code execution as the httpd process user (often root on embedded systems), enabling firmware modification, traffic interception, lateral movement to other network devices, or use of the router as an attack platform. Real-world exploitation likelihood is HIGH given public disclosure.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

No patch listed yet 0.4% exploitation probability (EPSS)

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AnalysisAI

A critical stack-based buffer overflow vulnerability exists in Tenda O3V2 firmware version 1.0.0.12(3880) in the MAC filter modification function. An authenticated remote attacker can exploit improper input validation of the 'mac' parameter to achieve remote code execution with full system compromise (confidentiality, integrity, and availability impact). The vulnerability has public exploit disclosure and demonstrates high real-world exploitability.

RemediationAI

Contact Tenda support or check their official website for firmware updates beyond version 1.0.0.12(3880). Firmware updates should include bounds checking fixes in the fromMacFilterModify function.; priority: Critical - Apply immediately Workaround: Restrict access to the router's web interface (httpd) to trusted networks only. Disable remote management if enabled. Use a firewall rule to block external access to the management interface (typically port 80/443).; priority: Temporary mitigation pending patch Detection: Monitor httpd logs for unusual requests to /goform/operateMacFilter endpoint, especially those with oversized or malformed 'mac' parameter values. Look for stack traces or unexpected service crashes.; priority: Ongoing Access Control: Enforce strong authentication credentials on router admin accounts and disable default credentials. Limit which devices/users can authenticate to the router.; priority: High

Affected VersionsENISA

O3V2 1.0.0.12(3880)

Affects your stack

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Technical ContextAI · show details

The vulnerability resides in the httpd web server component of Tenda O3V2 router firmware, specifically in the fromMacFilterModify function handling requests to /goform/operateMacFilter. The root cause is CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), manifesting as a classic stack-based buffer overflow. The mac parameter undergoes insufficient bounds checking before being written to a stack-allocated buffer, allowing an attacker to overflow the buffer and overwrite the stack frame, including return addresses and saved registers. This is a memory safety issue common in C/C++ firmware implementations lacking modern protections. The affected product is a wireless mesh router system where httpd processes user requests, making this directly network-accessible after authentication.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 8.8 HIGH

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

PoC Detected

Jul 16, 2025 - 16:43 vuln.today

Public exploit code

CVE Published

Jul 11, 2025 - 01:15 nvd

HIGH 8.8

DescriptionCVE.org

A vulnerability was found in Tenda O3V2 1.0.0.12(3880). It has been rated as critical. This issue affects the function fromMacFilterModify of the file /goform/operateMacFilter of the component httpd. The manipulation of the argument mac leads to stack-based buffer overflow. The attack may be initiated remotely. The exploit has been disclosed to the public and may be used.

Executive ViewAI

Why It Matters

A critical remote code execution vulnerability affects Tenda O3V2 routers (version 1.0.0.12) with no vendor patch currently available. Organizations using this device model face immediate risk of unauthorized access and network compromise, as public exploits are actively circulating. This requires urgent remediation to prevent potential data breach, service disruption, and lateral movement into corporate networks.

Business Impact: High

Compensating Controls

Disable the MAC filter feature (/goform/operateMacFilter) if not operationally required; implement network segmentation to isolate affected devices from sensitive assets; restrict administrative access to device management interfaces via firewall rules or VPN; deploy intrusion detection signatures to monitor for exploitation attempts; implement WAF rules blocking POST requests to /goform/operateMacFilter with suspicious MAC parameters; consider replacing the device with a patched or alternative vendor solution pending vendor patch availability.

Threat Intelligence Overview

EPSS Score

0.4%

Top 43% exploitable

Exploit

POC

Public exploit code exists

Data Quality

6 sources

Confidence: High

EUVD

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.

SignalValue

Severity HIGH

CISA KEV No

Public POC Yes

EPSS 0.4%

Patch available No

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

Poc

System Exposure· derived

Open

Automatable· derived

Human Impact

High

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +44

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Buffer Overflow HIGH

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.