CVE-2026-3870: CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') in Zyxel VMG4005-B50B firmware
A buffer overflow vulnerability exists in the UPnP AddPortMapping() 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 vulnerability is classified as CWE-120, indicating a classic buffer overflow due to lack of input size checking.
AI Analysis
Technical Summary
CVE-2026-3870 is a buffer overflow vulnerability in the UPnP AddPortMapping() command of Zyxel VMG4005-B50B firmware. The flaw arises from copying input data without verifying its size, which can be triggered by an adjacent attacker. Exploitation leads to a temporary denial-of-service condition impacting the UPnP service on the affected device. The vulnerability affects firmware versions up to and including 5.13(ABRL.5.4)C0. No official patch or remediation level has been published by Zyxel as of the data provided.
Potential Impact
Successful exploitation results in a temporary denial-of-service condition on the UPnP function of the Zyxel VMG4005-B50B device. There is no indication of confidentiality or integrity impact. The attack requires adjacency, meaning the attacker must be on the same local network segment. The CVSS v3.1 base score is 6.5 (medium severity), reflecting the limited scope and impact of the vulnerability.
Mitigation Recommendations
No official patch or remediation has been published by Zyxel for this vulnerability. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, network administrators should consider restricting UPnP access to trusted devices only or disabling UPnP if it is not required to reduce exposure.
CVE-2026-3870: CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') in Zyxel VMG4005-B50B firmware
Description
A buffer overflow vulnerability exists in the UPnP AddPortMapping() 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 vulnerability is classified as CWE-120, indicating a classic buffer overflow due to lack of input size checking.
CVSS v3.1
Score 6.5medium
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-3870 is a buffer overflow vulnerability in the UPnP AddPortMapping() command of Zyxel VMG4005-B50B firmware. The flaw arises from copying input data without verifying its size, which can be triggered by an adjacent attacker. Exploitation leads to a temporary denial-of-service condition impacting the UPnP service on the affected device. The vulnerability affects firmware versions up to and including 5.13(ABRL.5.4)C0. No official patch or remediation level has been published by Zyxel as of the data provided.
Potential Impact
Successful exploitation results in a temporary denial-of-service condition on the UPnP function of the Zyxel VMG4005-B50B device. There is no indication of confidentiality or integrity impact. The attack requires adjacency, meaning the attacker must be on the same local network segment. The CVSS v3.1 base score is 6.5 (medium severity), reflecting the limited scope and impact of the vulnerability.
Mitigation Recommendations
No official patch or remediation has been published by Zyxel for this vulnerability. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, network administrators should consider restricting UPnP access to trusted devices only or disabling UPnP if it is not required to reduce exposure.
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: 06/02/2026, 02:33:35 UTC
Last enriched: 06/09/2026, 09:51:29 UTC
Last updated: 07/31/2026, 19:22:58 UTC
Views: 131
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