How severe is CVE-2021-43787?

CVE-2021-43787 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-43787?

CVE-2021-43787 affects the following packages: nodebb (npm). Ecosystems affected: npm.

How do I fix CVE-2021-43787?

Update nodebb to 1.18.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-43787 is resolved across your whole dependency graph.

How do I detect CVE-2021-43787 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nodebb, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-43787 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2021-43787 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-43787, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-43787?

CVE-2021-43787 has an EPSS (Exploit Prediction Scoring System) score of 1.3%, placing it in the 70th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-43787?

CVE-2021-43787 is classified as Cross-site Scripting (XSS) (CWE-79), CWE-1321 (CWE-1321). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2021-43787 published, and has it been updated?

CVE-2021-43787 was published on November 29, 2021 and was last updated on July 9, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

MEDIUM severity

CVE-2021-43787 — nodebb

MEDIUMFix: NodeBB/NodeBB@1783f91

CVE-2021-43787 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in nodebb. 1 public exploit reference exists, so weaponization risk is real. A fix is available for nodebb — see the affected versions and patch details below.

XSS via prototype pollution in NodeBB

Also known asGHSA-wx69-rvg3-x7fc

Published

Nov 29, 2021

Updated

Jul 9, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs70th percentile — riskier than 70% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-43787 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

0other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

nodebbnpm

266downloads / week

Description

Impact

A prototype pollution vulnerability in the uploader module allowed a malicious user to inject arbitrary data (i.e. javascript) into the DOM, theoretically allowing for an account takeover when used in conjunction with a path traversal vulnerability disclosed at the same time as this report.

Patches

The vulnerability has been patched as of v1.18.5.

Workarounds

Cherry-pick commit hash 1783f918bc19568f421473824461ff2ed7755e4c to receive this patch in lieu of a full upgrade.

For more information

If you have any questions or comments about this advisory:

Email us at [email protected]

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`nodebb`	≥ 1.15.0&&< 1.18.5	1.18.5`npm install nodebb@1.18.5`

Affected Products

1 product · 1 configurations

Application

nodebbnodebb

≥ 1.15.5 && ≤ 1.18.4

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Nodebb is an open source Node.js based forum software. In affected versi…

blog.sonarsource.comNVDOct 2022

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nodebb, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update nodebb to 1.18.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-43787 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### Impact A prototype pollution vulnerability in the uploader module allowed a malicious user to inject arbitrary data (i.e. javascript) into the DOM, theoretically allowing for an account takeover when used in conjunction with a path traversal vulnerability disclosed at the same time as this report. ### Patches The vulnerability has been patched as of v1.18.5. ### Workarounds Cherry-pick commit hash 1783f918bc19568f421473824461ff2ed7755e4c to receive this patch in lieu of a full upgrade. ### For more information If you have any questions or comments about this advisory: * Email us at [sec