CVE-2026-3870: CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') in Zyxel VMG4005-B50B firmware
CVE-2026-3870 is a buffer overflow vulnerability in the UPnP AddPortMapping() command of Zyxel VMG4005-B50B firmware versions up to 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 vulnerability does not impact confidentiality or integrity but affects availability. No official patch or remediation guidance has been provided by Zyxel as of the publication date. The vulnerability has a medium severity rating with a CVSS score of 6. 5. 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 AddPortMapping() command of the UPnP service on Zyxel VMG4005-B50B firmware versions up to 5.13(ABRL.5.4)C0. An adjacent attacker can trigger this overflow to cause a temporary denial-of-service condition, disrupting the UPnP functionality. The vulnerability is rated medium severity with a CVSS 3.1 score of 6.5, reflecting its impact on availability only. No official patch or remediation level has been disclosed by Zyxel, and no exploits are currently known in the wild.
Potential Impact
The vulnerability allows an adjacent attacker to cause a temporary denial-of-service condition on the UPnP service of affected Zyxel VMG4005-B50B devices. There is no impact on confidentiality or integrity. The disruption affects device availability specifically related to UPnP functionality.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official fix or remediation level has been published by Zyxel, users should monitor Zyxel's advisories for updates. Until a patch is available, limiting UPnP exposure to untrusted adjacent networks may reduce risk.
CVE-2026-3870: CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') in Zyxel VMG4005-B50B firmware
Description
CVE-2026-3870 is a buffer overflow vulnerability in the UPnP AddPortMapping() command of Zyxel VMG4005-B50B firmware versions up to 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 vulnerability does not impact confidentiality or integrity but affects availability. No official patch or remediation guidance has been provided by Zyxel as of the publication date. The vulnerability has a medium severity rating with a CVSS score of 6. 5. 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 AddPortMapping() command of the UPnP service on Zyxel VMG4005-B50B firmware versions up to 5.13(ABRL.5.4)C0. An adjacent attacker can trigger this overflow to cause a temporary denial-of-service condition, disrupting the UPnP functionality. The vulnerability is rated medium severity with a CVSS 3.1 score of 6.5, reflecting its impact on availability only. No official patch or remediation level has been disclosed by Zyxel, and no exploits are currently known in the wild.
Potential Impact
The vulnerability allows an adjacent attacker to cause a temporary denial-of-service condition on the UPnP service of affected Zyxel VMG4005-B50B devices. There is no impact on confidentiality or integrity. The disruption affects device availability specifically related to UPnP functionality.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official fix or remediation level has been published by Zyxel, users should monitor Zyxel's advisories for updates. Until a patch is available, limiting UPnP exposure to untrusted adjacent networks may reduce risk.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- Zyxel
- Date Reserved
- 2026-03-10T08:42:15.293Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a1e40ffe29bf47b506f6bc6
Added to database: 6/2/2026, 2:33:35 AM
Last enriched: 6/2/2026, 2:48:33 AM
Last updated: 6/2/2026, 4:47:56 AM
Views: 5
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