CVE-2026-3871: CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') in Zyxel VMG4005-B50B firmware
CVE-2026-3871 is a buffer overflow vulnerability in the UPnP DeletePortMapping() command of Zyxel VMG4005-B50B firmware versions up to and including 5.13(ABRL.5.4)C0. This vulnerability can be exploited by an adjacent attacker to cause a temporary denial-of-service (DoS) condition affecting the UPnP functionality of the device. The issue stems from improper size checking during buffer copy operations.
AI Analysis
Technical Summary
This vulnerability involves a classic buffer overflow (CWE-120) in the Zyxel VMG4005-B50B firmware's UPnP DeletePortMapping() command. Versions up to 5.13(ABRL.5.4)C0 are affected. An adjacent attacker can exploit this flaw to trigger a temporary DoS by overflowing a buffer due to lack of input size validation. The vulnerability does not impact confidentiality or integrity but results in availability disruption of the UPnP service. No official patch or remediation level has been published by Zyxel as of the data provided.
Potential Impact
The vulnerability allows an adjacent attacker to cause a temporary denial-of-service condition on the UPnP function of the affected Zyxel VMG4005-B50B devices. There is no indication of confidentiality or integrity compromise. The impact is limited to availability disruption of the UPnP service.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official fix or remediation level is provided, users should monitor Zyxel's advisories for updates. In the meantime, limiting UPnP exposure to untrusted networks or disabling UPnP if not required may reduce risk.
CVE-2026-3871: CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') in Zyxel VMG4005-B50B firmware
Description
CVE-2026-3871 is a buffer overflow vulnerability in the UPnP DeletePortMapping() command of Zyxel VMG4005-B50B firmware versions up to and including 5.13(ABRL.5.4)C0. This vulnerability can be exploited by an adjacent attacker to cause a temporary denial-of-service (DoS) condition affecting the UPnP functionality of the device. The issue stems from improper size checking during buffer copy operations.
CVSS v3.1
Score 6.5medium
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability involves a classic buffer overflow (CWE-120) in the Zyxel VMG4005-B50B firmware's UPnP DeletePortMapping() command. Versions up to 5.13(ABRL.5.4)C0 are affected. An adjacent attacker can exploit this flaw to trigger a temporary DoS by overflowing a buffer due to lack of input size validation. The vulnerability does not impact confidentiality or integrity but results in availability disruption of the UPnP service. No official patch or remediation level has been published by Zyxel as of the data provided.
Potential Impact
The vulnerability allows an adjacent attacker to cause a temporary denial-of-service condition on the UPnP function of the affected Zyxel VMG4005-B50B devices. There is no indication of confidentiality or integrity compromise. The impact is limited to availability disruption of the UPnP service.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official fix or remediation level is provided, users should monitor Zyxel's advisories for updates. In the meantime, limiting UPnP exposure to untrusted networks or disabling UPnP if not required may reduce risk.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- Zyxel
- Date Reserved
- 2026-03-10T08:42:18.809Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a1e40ffe29bf47b506f6bc9
Added to database: 06/02/2026, 02:33:35 UTC
Last enriched: 06/09/2026, 09:51:47 UTC
Last updated: 07/31/2026, 19:22:58 UTC
Views: 138
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