SB2026060223 - Multiple vulnerabilities in Zyxel products

Description

This security bulletin contains information about 2 vulnerabilities.

1) Buffer overflow (CVE-ID: CVE-2026-3870)

CWE-ID: CWE-119 - Memory corruption

CVSSv4: CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to a boundary error in the UPnP AddPortMapping() command. A remote attacker on the local network can trigger memory corruption and cause a denial of service condition on the target system.

2) Buffer overflow (CVE-ID: CVE-2026-3871)

CWE-ID: CWE-119 - Memory corruption

CVSSv4: CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to a boundary error in the UPnP DeletePortMapping() command. A remote attacker on the local network can trigger memory corruption and cause a denial of service condition on the target system.

Remediation

Install update from vendor's website.

References

• 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