# CVE-2019-9955: Cross-site scripting in n/a

> Attackers can execute arbitrary scripts in the victim's browser via the firewall login page, potentially stealing session cookies or credentials.

- **Severity:** Medium 6.1 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 22 Apr 2019
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-9r2m-gm27-q4jp

## What is CVE-2019-9955?

CVE-2019-9955 is a medium-severity cross-site scripting vulnerability in n/a, published on 22 Apr 2019. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2019-9955?

It affects 21 products.


Products: Zyxel Atp200 Firmware, Zyxel Atp500 Firmware, Zyxel Atp800 Firmware, Zyxel Usg1100 Firmware, Zyxel Usg110 Firmware, Zyxel Usg1900 Firmware, Zyxel Usg20-Vpn Firmware, Zyxel Usg20w-Vpn Firmware, Zyxel Usg210 Firmware, Zyxel Usg2200-Vpn Firmware, Zyxel Usg310 Firmware, Zyxel Usg40 Firmware, Zyxel Usg40w Firmware, Zyxel Usg60 Firmware, Zyxel Usg60w Firmware, Zyxel Vpn100 Firmware, Zyxel Vpn300 Firmware, Zyxel Vpn50 Firmware, Zyxel Zywall 1100 Firmware, Zyxel Zywall 110 Firmware and 1 more.

## How do I fix CVE-2019-9955?

No fix has been published for CVE-2019-9955 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-9955 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2019-9955 exists.

Public exploit code:

- Zyxel ZyWall 310 / ZyWall 110 / USG1900 / ATP500 / USG40 - Login Page Cross-Site Scripting (exploitdb)
- Zyxel - Cross-Site Scripting (nuclei): http/cves/2019/CVE-2019-9955.yaml

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-9955 and fix it if it is affected.

What it is: CVE-2019-9955 is a medium-severity cross-site scripting vulnerability in n/a, published on 22 Apr 2019. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2019-9955 exists.

Affected product: n/a. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2019-9955/ (Markdown: https://insights.sbomify.com/CVE-2019-9955/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-9955
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-9955
- OSV: https://osv.dev/vulnerability/CVE-2019-9955

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From sbomify Insights: https://insights.sbomify.com/CVE-2019-9955/
Summaries are generated and may contain mistakes; the official description above is the record.