Package Instance

undici Denial of Service attack via bad certificate data
### Impact

Applications that use undici to implement a webhook-like system are vulnerable. If the attacker set up a server with an invalid certificate, and they can force the application to call the webhook repeatedly, then they can cause a memory leak. 

### Patches

This has been patched in https://github.com/nodejs/undici/pull/4088.

### Workarounds

If a webhook fails, avoid keep calling it repeatedly.

### References

Reported as: https://github.com/nodejs/undici/issues/3895

fetch(url) leads to a memory leak in undici
### Impact

Calling `fetch(url)` and not consuming the incoming body ((or consuming it very slowing) will lead to a memory leak. 

### Patches

Patched in v6.6.1

### Workarounds

Make sure to always consume the incoming body.

Undici has Unhandled Exception in WebSocket Client Due to Invalid server_max_window_bits Validation
### Impact

The undici WebSocket client is vulnerable to a denial-of-service attack due to improper validation of the `server_max_window_bits` parameter in the permessage-deflate extension. When a WebSocket client connects to a server, it automatically advertises support for permessage-deflate compression. A malicious server can respond with an out-of-range `server_max_window_bits` value (outside zlib's valid range of 8-15). When the server subsequently sends a compressed frame, the client attempts to create a zlib InflateRaw instance with the invalid windowBits value, causing a synchronous RangeError exception that is not caught, resulting in immediate process termination.

The vulnerability exists because:

1. The `isValidClientWindowBits()` function only validates that the value contains ASCII digits, not that it falls within the valid range 8-15
2. The `createInflateRaw()` call is not wrapped in a try-catch block
3. The resulting exception propagates up through the call stack and crashes the Node.js process

### Patches
_Has the problem been patched? What versions should users upgrade to?_

### Workarounds
_Is there a way for users to fix or remediate the vulnerability without upgrading?_

Undici has an HTTP Request/Response Smuggling issue
### Impact

Undici allows duplicate HTTP `Content-Length` headers when they are provided in an array with case-variant names (e.g., `Content-Length` and `content-length`). This produces malformed HTTP/1.1 requests with multiple conflicting `Content-Length` values on the wire.

**Who is impacted:**
  - Applications using `undici.request()`, `undici.Client`, or similar low-level APIs with headers passed as flat arrays
  - Applications that accept user-controlled header names without case-normalization

**Potential consequences:**
  - **Denial of Service**: Strict HTTP parsers (proxies, servers) will reject requests with duplicate `Content-Length` headers (400 Bad Request)
  - **HTTP Request Smuggling**: In deployments where an intermediary and backend interpret duplicate headers inconsistently (e.g., one uses the first value, the other uses the last), this can enable request smuggling attacks leading to ACL bypass, cache poisoning, or credential hijacking

### Patches

 Patched in the undici version v7.24.0 and v6.24.0. Users should upgrade to this version or later.

### Workarounds

  If upgrading is not immediately possible:

  1. **Validate header names**: Ensure no duplicate `Content-Length` headers (case-insensitive) are present before passing headers to undici
  2. **Use object format**: Pass headers as a plain object (`{ 'content-length': '123' }`) rather than an array, which naturally deduplicates by key
  3. **Sanitize user input**: If headers originate from user input, normalize header names to lowercase and reject duplicates

Use of Insufficiently Random Values in undici
### Impact

[Undici `fetch()` uses Math.random()](https://github.com/nodejs/undici/blob/8b06b8250907d92fead664b3368f1d2aa27c1f35/lib/web/fetch/body.js#L113) to choose the boundary for a multipart/form-data request. It is known that the output of Math.random() can be predicted if several of its generated values are known.

If there is a mechanism in an app that sends multipart requests to an attacker-controlled website, they can use this to leak the necessary values. Therefore, An attacker can tamper with the requests going to the backend APIs if certain conditions are met.

### Patches

This is fixed in 5.28.5; 6.21.1; 7.2.3.

### Workarounds

Do not issue multipart requests to attacker controlled servers.

### References

* https://hackerone.com/reports/2913312
* https://blog.securityevaluators.com/hacking-the-javascript-lottery-80cc437e3b7f

Undici has CRLF Injection in undici via `upgrade` option
### Impact

When an application passes user-controlled input to the `upgrade` option of `client.request()`, an attacker can inject CRLF sequences (`\r\n`) to:

1. Inject arbitrary HTTP headers
2. Terminate the HTTP request prematurely and smuggle raw data to non-HTTP services (Redis, Memcached, Elasticsearch)

The vulnerability exists because undici writes the `upgrade` value directly to the socket without validating for invalid header characters:

```javascript
// lib/dispatcher/client-h1.js:1121
if (upgrade) {
  header += `connection: upgrade\r\nupgrade: ${upgrade}\r\n`
}
```

### Patches

 Patched in the undici version v7.24.0 and v6.24.0. Users should upgrade to this version or later.

### Workarounds

Sanitize the `upgrade` option string before passing to undici:

```javascript
function sanitizeUpgrade(value) {
  if (/[\r\n]/.test(value)) {
    throw new Error('Invalid upgrade value')
  }
  return value
}

client.request({
  upgrade: sanitizeUpgrade(userInput)
})
```

Undici has Unbounded Memory Consumption in WebSocket permessage-deflate Decompression
## Description

The undici WebSocket client is vulnerable to a denial-of-service attack via unbounded memory consumption during permessage-deflate decompression. When a WebSocket connection negotiates the permessage-deflate extension, the client decompresses incoming compressed frames without enforcing any limit on the decompressed data size. A malicious WebSocket server can send a small compressed frame (a "decompression bomb") that expands to an extremely large size in memory, causing the Node.js process to exhaust available memory and crash or become unresponsive.

The vulnerability exists in the `PerMessageDeflate.decompress()` method, which accumulates all decompressed chunks in memory and concatenates them into a single Buffer without checking whether the total size exceeds a safe threshold.

## Impact

- Remote denial of service against any Node.js application using undici's WebSocket client
- A single compressed WebSocket frame of ~6 MB can decompress to ~1 GB or more
- Memory exhaustion occurs in native/external memory, bypassing V8 heap limits
- No application-level mitigation is possible as decompression occurs before message delivery

### Patches

Users should upgrade to fixed versions.

### Workarounds

No workaround are possible.

Undici's Proxy-Authorization header not cleared on cross-origin redirect for dispatch, request, stream, pipeline
### Impact

Undici cleared Authorization and Proxy-Authorization headers for `fetch()`, but did not clear them for `undici.request()`.

### Patches

This has been patched in https://github.com/nodejs/undici/commit/6805746680d27a5369d7fb67bc05f95a28247d75.
Fixes has been released in v5.28.4 and v6.11.1.

### Workarounds

use `fetch()` or disable `maxRedirections`.

### References

Linzi Shang reported this.

* https://hackerone.com/reports/2408074
* https://github.com/nodejs/undici/security/advisories/GHSA-3787-6prv-h9w3