CVE-2021-32702 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in @auth0/nextjs-auth0. A fix is available for @auth0/nextjs-auth0 — see the affected versions and patch details below.
Reflected XSS from the callback handler's error query parameter
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2021-32702 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
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.
@auth0/nextjs-auth0npmDescription
Overview
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.
Am I affected?
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.
How to fix that?
Upgrade to version 1.4.2.
Will this update impact my users?
The fix adds basic HTML escaping to the error message and it should not impact your users.
Credit
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @auth0/nextjs-auth0 | all versions | 1.4.2npm install @auth0/nextjs-auth0@1.4.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @auth0/nextjs-auth0, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @auth0/nextjs-auth0 to 1.4.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-32702 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2021-32702 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-32702. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-32702 in your dependencies?
O3 Security finds CVE-2021-32702 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.