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 5. 13(ABRL. 5. 4)C0. This flaw can be exploited by an adjacent attacker to cause a temporary denial-of-service (DoS) affecting the UPnP functionality of the device. The vulnerability does not impact confidentiality or integrity but results in availability disruption. No official patch or remediation guidance is currently available from the vendor. There are no known exploits in the wild at this time.
AI Analysis
Technical Summary
This vulnerability is a classic buffer overflow (CWE-120) in the UPnP DeletePortMapping() command implementation in Zyxel VMG4005-B50B firmware versions up to 5.13(ABRL.5.4)C0. An attacker with adjacent network access can trigger this overflow to cause a temporary denial-of-service condition by disrupting the UPnP service on the device. The CVSS 3.1 base score is 6.5, reflecting medium severity with attack vector as adjacent network, low attack complexity, no privileges required, no user interaction, and impact limited to availability.
Potential Impact
Successful exploitation results in a temporary denial-of-service condition affecting the UPnP functionality of the Zyxel VMG4005-B50B device. There is no impact on confidentiality or integrity. The device’s availability for UPnP operations is disrupted until recovery.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, network administrators should consider restricting access to the UPnP service from untrusted adjacent networks to reduce exposure. Monitor vendor channels for updates and apply patches promptly once available.
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 5. 13(ABRL. 5. 4)C0. This flaw can be exploited by an adjacent attacker to cause a temporary denial-of-service (DoS) affecting the UPnP functionality of the device. The vulnerability does not impact confidentiality or integrity but results in availability disruption. No official patch or remediation guidance is currently available from the vendor. There are no known exploits in the wild at this time.
CVSS v3.1
Score 6.5medium
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability is a classic buffer overflow (CWE-120) in the UPnP DeletePortMapping() command implementation in Zyxel VMG4005-B50B firmware versions up to 5.13(ABRL.5.4)C0. An attacker with adjacent network access can trigger this overflow to cause a temporary denial-of-service condition by disrupting the UPnP service on the device. The CVSS 3.1 base score is 6.5, reflecting medium severity with attack vector as adjacent network, low attack complexity, no privileges required, no user interaction, and impact limited to availability.
Potential Impact
Successful exploitation results in a temporary denial-of-service condition affecting the UPnP functionality of the Zyxel VMG4005-B50B device. There is no impact on confidentiality or integrity. The device’s availability for UPnP operations is disrupted until recovery.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, network administrators should consider restricting access to the UPnP service from untrusted adjacent networks to reduce exposure. Monitor vendor channels for updates and apply patches promptly once available.
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: 6/2/2026, 2:33:35 AM
Last enriched: 6/2/2026, 2:48:26 AM
Last updated: 6/2/2026, 4:45:38 AM
Views: 15
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