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6.5
MEDIUM CVSS 3.1
CVE-2026-3871
Zyxel UPnP Buffer Overflow Denial-of-Service
Overview
Description

A buffer overflow vulnerability in the UPnP DeletePortMapping() command in Zyxel VMG4005-B50B firmware versions through 5.13(ABRL.5.4)C0 could allow an adjacent attacker to trigger a temporary denial-of-service (DoS) condition affecting the UPnP function of the affected device.

Details
INFO

Published Date :

June 2, 2026, 3:16 a.m.

Last Modified :

June 2, 2026, 3:16 a.m.

Remotely Exploit :

No

Source :

[email protected]
Impact
Affected Products

The following products are affected by CVE-2026-3871 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Zyxel vmg4005-b50b_firmware
: Total Affected Vendor : 1 | Products : 1
Scoring
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.
Score Version Severity Vector Exploitability Score Impact Score Source
CVSS 3.1 MEDIUM 96e50032-ad0d-4058-a115-4d2c13821f9f
CVSS 3.1 MEDIUM [email protected]
Solution
Update device firmware to patch a buffer overflow in the UPnP DeletePortMapping command.
  • Update Zyxel firmware to version 5.13(ABRL.5.4)C0 or later.
  • Disable UPnP if not strictly needed.
References
References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2026-3871.

URL Resource
https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-buffer-overflow-vulnerabilities-in-the-upnp-function-of-certain-4g-lte-5g-nr-cpe-and-dsl-ethernet-cpe-06-02-2026
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-3871 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-3871 weaknesses.

CAPEC-8: Buffer Overflow in an API Call Buffer Overflow in an API Call CAPEC-9: Buffer Overflow in Local Command-Line Utilities Buffer Overflow in Local Command-Line Utilities CAPEC-10: Buffer Overflow via Environment Variables Buffer Overflow via Environment Variables CAPEC-14: Client-side Injection-induced Buffer Overflow Client-side Injection-induced Buffer Overflow CAPEC-24: Filter Failure through Buffer Overflow Filter Failure through Buffer Overflow CAPEC-42: MIME Conversion MIME Conversion CAPEC-44: Overflow Binary Resource File Overflow Binary Resource File CAPEC-45: Buffer Overflow via Symbolic Links Buffer Overflow via Symbolic Links CAPEC-46: Overflow Variables and Tags Overflow Variables and Tags CAPEC-47: Buffer Overflow via Parameter Expansion Buffer Overflow via Parameter Expansion CAPEC-67: String Format Overflow in syslog() String Format Overflow in syslog() CAPEC-92: Forced Integer Overflow Forced Integer Overflow CAPEC-100: Overflow Buffers Overflow Buffers

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-3871 vulnerability anywhere in the article.

Results are limited to the first 20 news articles due to potential performance issues.

The following table lists the changes that have been made to the CVE-2026-3871 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • New CVE Received by [email protected]

    Jun. 02, 2026

    Action Type Old Value New Value
    Added Description A buffer overflow vulnerability in the UPnP DeletePortMapping() command in Zyxel VMG4005-B50B firmware versions through 5.13(ABRL.5.4)C0 could allow an adjacent attacker to trigger a temporary denial-of-service (DoS) condition affecting the UPnP function of the affected device.
    Added CVSS V3.1 AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
    Added CWE CWE-120
    Added Reference https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-buffer-overflow-vulnerabilities-in-the-upnp-function-of-certain-4g-lte-5g-nr-cpe-and-dsl-ethernet-cpe-06-02-2026
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
CVSS
Vulnerability Scoring Details
Base CVSS Score: 6.5
Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality Impact
Integrity Impact
Availability Impact