How severe is CVE-2019-9955?

CVE-2019-9955 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2019-9955 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 21% (97th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-9955?

CVE-2019-9955 primarily affects Zyxel Atp200 Firmware. In total, 21 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-9955?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2019-9955 published?

CVE-2019-9955 was published on 2019-04-22 and last updated on 2026-06-17.

CVE-2019-9955

CVE-2019-9955 is a medium-severity vulnerability in Zyxel Atp200 Firmware with a CVSS 3.x base score of 6.1. Its EPSS exploit-prediction score of 21% places it in the 97th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-79.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
CVSS v2: 4.3
EPSS exploit prediction: 21% (97th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Zyxel Atp200 Firmware
Published: 2019-04-22
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2019-9955?: 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.
How severe is CVE-2019-9955?: CVE-2019-9955 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2019-9955 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 21% (97th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-9955?: CVE-2019-9955 primarily affects Zyxel Atp200 Firmware. In total, 21 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-9955?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2019-9955 published?: CVE-2019-9955 was published on 2019-04-22 and last updated on 2026-06-17.

References

Affected products (21)

cpe:2.3:o:zyxel:atp200_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp500_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:atp800_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg20-vpn_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg20w-vpn_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg40_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg40w_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg60_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg60w_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg110_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg210_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg310_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg1100_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg1900_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:usg2200-vpn_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:zywall_110_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:zywall_310_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:zywall_1100_firmware:4.31:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:vpn50_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:vpn100_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:vpn300_firmware:-:*:*:*:*:*:*:*

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