PatchTheCVECVE-2021-3831: gnuboard5 is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'
CVE-2021-3831 is a medium-severity flaw (CVSS 6.1) affecting gnuboard5. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
gnuboard5 is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Why this priority
- Public exploit reference
A fixed release or distro patch exists.
Risk facts
| CVSS score | 6.1 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | Required |
| EPSS exploit chance | 1.8% (top 21%) |
| CISA exploited list | No |
| Weakness | CWE-79 |
| Published | 2021-12-14 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Public exploits and detection
Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.
- Nuclei scan template: Gnuboard 5 - Cross-Site Scripting
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-3831?
gnuboard5: upgrade to 5.4.20. Exact commands for each OS are on this page.
Is CVE-2021-3831 being exploited?
CVE-2021-3831 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2021-3831 affect?
CVE-2021-3831 affects gnuboard5. Severity is medium (CVSS 6.1). gnuboard5 is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
How urgent is CVE-2021-3831?
Priority 46/100. Public exploit reference