CVE-2021-21310
MEDIUMCVE-2021-21310 is a medium-severity (CVSS 5.9) CWE-290 vulnerability in next-auth. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2021-21310 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Token verification bug in next-auth
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.
next-authnpmDescription
NextAuth.js (next-auth) is am open source authentication solution for Next.js applications. In next-auth before version 3.3.0 there is a token verification vulnerability. Implementations using the Prisma database adapter in conjunction with the Email provider are impacted. Implementations using the Email provider with the default database adapter are not impacted. Implementations using the Prisma database adapter but not using the Email provider are not impacted. The Prisma database adapter was checking the verification token, but was not verifying the email address associated with that token. This made it possible to use a valid token to sign in as another user when using the Prima adapter in conjunction with the Email provider. This issue is specific to the community supported Prisma adapter. This issue is fixed in version 3.3.0.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | next-auth | all versions | 3.3.0 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for next-auth. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update next-auth to 3.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21310 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 pinpoints whether CVE-2021-21310 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2021-21310. 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-2021-21310 in your dependencies?
O3 detects CVE-2021-21310 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.