JWT authentication in a Next.js API with the Edge Runtime. JWTClaimValidationFailed: "nbf" claim timestamp check failed

Problem: JWT Claim Validation Error (nbf)

Recently, I encountered a problem while using JWT authentication in a Next.js API with the Edge Runtime. The error message was:

JWTClaimValidationFailed: "nbf" claim timestamp check failed

This error occurs because the JWT (JSON Web Token) has an nbf (Not Before) claim, which specifies the earliest time at which the JWT is valid. The issue is caused by slight time differences between the client and the Edge Runtime server, making the nbf value invalid.

Why This Happens

• The nbf claim in JWT is a timestamp indicating the earliest time the token is valid.

• If the server’s clock is slightly behind or ahead, the JWT might be considered invalid.

• This is a common issue in distributed environments, especially with serverless Edge functions.

Solution: Use Clock Tolerance in JWT Verification

To solve this problem, I added a clockTolerance option in the JWT verification process, which provides a small window of time to account for clock drift.

Updated Example JWT Verification Code

// src/pages/api/auth/verify.js
import * as jose from 'jose'

const jwtConfig = {
  secret: new TextEncoder().encode(process.env.BACKEND_JWT_SECRET)
}

export default async function handler(req, res) {
  if (req.method !== 'POST') {
    return res.status(405).json({ error: 'Method not allowed' })
  }

  try {
    let token = req.headers.authorization

    if (!token) {
      return res.status(401).json({ isAuthenticated: false, error: 'No token provided' })
    }

    if (token.startsWith('Bearer ')) {
      token = token.replace('Bearer ', '')
    }

    const decoded = await jose.jwtVerify(token, jwtConfig.secret, {
      clockTolerance: '5s' // Allows a 5-second tolerance for clock drift
    })

    if (decoded.payload) {
      return res.status(200).json({ isAuthenticated: true, user: decoded.payload })
    }
  } catch (err) {
    console.error('Token verification error:', err)
    return res.status(401).json({ isAuthenticated: false, error: 'Invalid token' })
  }
}

Why This Works

• The clockTolerance option in JWT verification allows a small window of time (5 seconds in this case) to account for slight time differences.

• This fix is especially useful in distributed environments like Edge Runtime.

Conclusion

If you are using JWT authentication in a distributed system or Edge Runtime environment, always consider using clockTolerance to avoid time synchronization issues.