CVE-2021-3831

MEDIUMNVD 6.16.1—Elevated

6.1

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

CVSS v3: 6.1
EG Score: 6.1(medium)
EPSS: 96.4%
KEV: Not listed

Published

December 14, 2021

Last Modified

November 21, 2024

References (4)

security@huntrhttps://github.com/gnuboard/gnuboard5/commit/2e81619ea87bc9c0b4a073d8df3c7693a6fdbf0d
security@huntrhttps://huntr.dev/bounties/25775287-88cd-4f00-b978-692d627dff04
af854a3a-2127-422b-91ae-364da2661108https://github.com/gnuboard/gnuboard5/commit/2e81619ea87bc9c0b4a073d8df3c7693a6fdbf0d
af854a3a-2127-422b-91ae-364da2661108https://huntr.dev/bounties/25775287-88cd-4f00-b978-692d627dff04

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-79Cross-site Scripting (XSS)

Data Freshness Timeline

(refreshed 7× in last 7d / 20× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

2026-06-07 15:23 UTCEPSS rescore
2026-06-07 15:23 UTCEPSS rescore
2026-06-06 13:46 UTCEPSS rescore
2026-06-06 13:46 UTCEPSS rescore
2026-06-05 22:45 UTCEPSS rescore
2026-06-04 13:10 UTCEPSS rescore
2026-06-04 13:10 UTCEPSS rescore
2026-06-02 20:11 UTCEPSS rescore
2026-06-02 20:11 UTCEPSS rescore
2026-06-01 13:50 UTCEPSS rescore
2026-06-01 13:50 UTCEPSS rescore
2026-05-31 22:29 UTCEPSS rescore
2026-05-31 22:29 UTCEPSS rescore
2026-05-31 00:15 UTCEPSS rescore
2026-05-31 00:15 UTCEPSS rescore
2026-05-29 13:42 UTCEPSS rescore
2026-05-28 13:43 UTCEPSS rescore
2026-05-28 13:43 UTCEPSS rescore
2026-05-27 13:39 UTCEPSS rescore
2026-05-27 13:39 UTCEPSS rescore

Publicly available exploits

(1 reference)

Working exploit code is in the public domain. Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

Nucleihttp/cves/2021/CVE-2021-3831.yaml
First seen Jan 1, 2021
Gnuboard 5 - Cross-Site Scripting
Open source ↗

Frequently asked(5)

What is CVE-2021-3831?

CVE-2021-3831 is a medium vulnerability published on December 14, 2021. gnuboard5 is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

When was CVE-2021-3831 disclosed?

CVE-2021-3831 was first published in the National Vulnerability Database on December 14, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-3831 actively exploited?

CVE-2021-3831 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 96.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-3831?

CVE-2021-3831 has a CVSS v3 base score of 6.1 (NVD).

How do I remediate CVE-2021-3831?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-3831, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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CVE-2021-3831

📅 Published

🔄 Last Modified

🔗 References (4)

Weakness Classification(1)

Data Freshness Timeline

Publicly available exploits

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-3831?

🔗 Related CVEs(same CWE)

Same CWE

Published

Last Modified

References (4)

Frequently asked(5)

Related CVEs(same CWE)