CVE-2019-9955

Severity: medium (CVSS 6.1 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 21.2% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2019-04-22 · updated 2026-06-17
Weakness: CWE-79

Description

On Zyxel ATP200, ATP500, ATP800, USG20-VPN, USG20W-VPN, USG40, USG40W, USG60, USG60W, USG110, USG210, USG310, USG1100, USG1900, USG2200-VPN, ZyWALL 110, ZyWALL 310, ZyWALL 1100 devices, the security firewall login page is vulnerable to Reflected XSS via the unsanitized 'mp_idx' parameter.

Affected products

Zyxel Atp200 Firmware: 4.31
Zyxel Atp500 Firmware: 4.31
Zyxel Atp800 Firmware: 4.31
Zyxel Usg1100 Firmware: 4.31
Zyxel Usg110 Firmware: 4.31
Zyxel Usg1900 Firmware: 4.31
Zyxel Usg20-Vpn Firmware: 4.31
Zyxel USG20(W)-VPN firmware: 4.31
Zyxel Usg210 Firmware: 4.31
Zyxel Usg2200-Vpn Firmware: 4.31
Zyxel Usg310 Firmware: 4.31
Zyxel Usg40 Firmware: 4.31
Zyxel Usg40W Firmware: 4.31
Zyxel Usg60 Firmware: 4.31
Zyxel Usg60W Firmware: 4.31
Zyxel Vpn100 Firmware: all versions
Zyxel Vpn300 Firmware: all versions
Zyxel Vpn50 Firmware: all versions
Zyxel Zywall 1100 Firmware: 4.31
Zyxel Zywall 110 Firmware: 4.31
Zyxel Zywall 310 Firmware: 4.31

References

http://packetstormsecurity.com/files/152525/Zyxel-ZyWall-Cross-Site-Scripting.html
http://seclists.org/fulldisclosure/2019/Apr/22
https://www.exploit-db.com/exploits/46706/
https://www.securitymetrics.com/blog/Zyxel-Devices-Vulnerable-Cross-Site-Scripting-Login-page
https://www.zyxel.com/support/reflected-cross-site-scripting-vulnerability-of-firewalls.shtml
http://packetstormsecurity.com/files/152525/Zyxel-ZyWall-Cross-Site-Scripting.html
http://seclists.org/fulldisclosure/2019/Apr/22
https://www.exploit-db.com/exploits/46706/
https://www.securitymetrics.com/blog/Zyxel-Devices-Vulnerable-Cross-Site-Scripting-Login-page
https://www.zyxel.com/support/reflected-cross-site-scripting-vulnerability-of-firewalls.shtml

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