Audit JSON Web Tokens (JWT) for security vulnerabilities (alg: "none"
Audit JSON Web Tokens (JWT) for security vulnerabilities (alg: "none", weak HMAC keys, expired claims, sensitive data leaks) per RFC 7519 & RFC 8725
Request
- x-api-key: <your-api-key>
- Content-Type: application/json
Response
{
"claimsAudit": {
"audience": "<audience>",
"expirationTime": "10:00",
"hasReplayProtectionJti": true,
"isExpired": true,
"isNotBeforeValid": true,
"issuedAtTime": "10:00",
"issuer": "Santander Bank Polska",
"notBeforeTime": "10:00",
"subject": "Your September invoice"
},
"isSecure": true,
"securityFindings": [
{
"code": "ABC-123",
"message": "Hello from castomAPI.",
"remediation": "<remediation>",
"severity": "CRITICAL"
}
],
"securityScore": 0,
"status": "success",
"tokenStructure": {
"algorithm": "<algorithm>",
"hasSignature": true,
"headerClaims": {},
"payloadClaims": {},
"tokenType": "standard"
},
"tokensDeducted": 1,
"vulnerabilityLevel": "SECURE"
}What it does
Audit JSON Web Tokens (JWT) for security vulnerabilities (alg: "none", weak HMAC keys, expired claims, sensitive data leaks) per RFC 7519 & RFC 8725
Request
Body
| Field | Type | Required | Description |
|---|---|---|---|
clockSkewSeconds | integer | no | Allowed clock skew tolerance in seconds for timestamp validation (default: 60s) |
token | string | yes | The raw encoded JSON Web Token string to inspect |
Example request
{
"clockSkewSeconds": 60,
"token": "<token>"
}Response
| Field | Type | Description |
|---|---|---|
claimsAudit | object | |
↳ audience | string | |
↳ expirationTime | string | |
↳ hasReplayProtectionJti | boolean | |
↳ isExpired | boolean | |
↳ isNotBeforeValid | boolean | |
↳ issuedAtTime | string | |
↳ issuer | string | |
↳ notBeforeTime | string | |
↳ subject | string | |
isSecure | boolean | |
securityFindings | array<object> | |
↳ code | string | |
↳ message | string | |
↳ remediation | string | |
↳ severity | enum | One of: CRITICAL, HIGH, MEDIUM, LOW, INFO. |
securityScore | integer | |
status | string | |
tokenStructure | object | |
↳ algorithm | string | |
↳ hasSignature | boolean | |
↳ headerClaims | object | |
↳ payloadClaims | object | |
↳ tokenType | string | |
tokensDeducted | integer | |
vulnerabilityLevel | enum | One of: SECURE, LOW_RISK, MEDIUM_RISK, CRITICAL_VULNERABILITY. |
Example response
{
"claimsAudit": {
"audience": "<audience>",
"expirationTime": "10:00",
"hasReplayProtectionJti": true,
"isExpired": true,
"isNotBeforeValid": true,
"issuedAtTime": "10:00",
"issuer": "Santander Bank Polska",
"notBeforeTime": "10:00",
"subject": "Your September invoice"
},
"isSecure": true,
"securityFindings": [
{
"code": "ABC-123",
"message": "Hello from castomAPI.",
"remediation": "<remediation>",
"severity": "CRITICAL"
}
],
"securityScore": 0,
"status": "success",
"tokenStructure": {
"algorithm": "<algorithm>",
"hasSignature": true,
"headerClaims": {},
"payloadClaims": {},
"tokenType": "standard"
},
"tokensDeducted": 1,
"vulnerabilityLevel": "SECURE"
}Errors
Every error answers with the same envelope: an HTTP status, a machine code and a sentence.
400 | The body or a parameter failed validation. The details array names the field. |
401 | No key, a revoked key or a wrong header. Send x-api-key. |
402 | The wallet cannot cover this call. Top up or wait for the monthly grant. |
404 | The resource does not exist, or it is not yours. Both answer identically and cost nothing. |
429 | Over the per-minute quota of your tier. Back off and retry. |
5xx | Upstream refused or timed out. The call is not billed. |
Code
curl -X POST 'https://app.castomapi.com/v1/verify/jwt' \
-H 'x-api-key: <your-api-key>' \
-H 'Content-Type: application/json' \
-d '{"clockSkewSeconds": 60, "token": "<token>"}'const res = await fetch('https://app.castomapi.com/v1/verify/jwt', {
method: 'POST',
headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
body: JSON.stringify({"clockSkewSeconds": 60, "token": "<token>"})
});
const data = await res.json();
console.log(data);import { request } from 'node:https';
// Node 18+ has fetch built in
const res = await fetch('https://app.castomapi.com/v1/verify/jwt', {
method: 'POST',
headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
body: JSON.stringify({"clockSkewSeconds": 60, "token": "<token>"})
});
const data = await res.json();
console.log(data);import requests
res = requests.post(
'https://app.castomapi.com/v1/verify/jwt',
headers={'x-api-key': '<your-api-key>'},
json={"clockSkewSeconds": 60, "token": "<token>"},
timeout=30,
)
print(res.json())<?php
$ch = curl_init('https://app.castomapi.com/v1/verify/jwt');
curl_setopt_array($ch, [
CURLOPT_CUSTOMREQUEST => 'POST',
CURLOPT_RETURNTRANSFER => true,
CURLOPT_HTTPHEADER => ['x-api-key: <your-api-key>', 'Content-Type: application/json'],
CURLOPT_POSTFIELDS => json_encode(['clockSkewSeconds' => 60, 'token' => '<token>']),
]);
$data = json_decode(curl_exec($ch), true);
print_r($data);Cost and limits
This operation needs no API key and costs nothing: called without a key it answers 200 and deducts zero tokens, up to 10 requests a minute per IP address.
Rate limits per minute
| No key | 10 |
| Free | 60 |
| Pro | 300 |
| Enterprise | 1200 |
Questions
What does Audit JSON Web Tokens (JWT) for security vulnerabilities (alg: "none" cost?
This operation needs no API key and costs nothing: called without a key it answers 200 and deducts zero tokens, up to 10 requests a minute per IP address.
How do I authenticate?
Send your key in the x-api-key header. One key covers every metered endpoint; there is nothing to enable per endpoint.
Can I send an Authorization: Bearer token instead?
Not for a metered endpoint — those take the x-api-key header and nothing else. Bearer tokens belong to the account side: the dashboard and account APIs accept a JWT session, and castomapi-auth issues those through a standard OAuth2 handshake, with authorization code, client credentials and refresh grants. The auth service page covers it.
What are the limits?
10 requests a minute per IP with no key at all, 60 a minute on the free tier, 300 on Pro, 1200 on Enterprise. Above the no-key tier the quota is per account, across every endpoint.
OpenAPI: https://app.castomapi.com/docs/json