tiny-secp256k1 is a tiny secp256k1 native/JS wrapper. Prior to version 1.1.7, a private key can be extracted on signing a malicious JSON-stringifiable object, when global Buffer is the buffer package. This affects only environments where require('buffer') is the NPM buffer package. The Buffer.isBuffer check can be bypassed, resulting in k reuse for different messages, leading to private key extraction over a single invalid message (and a second one for which any message/signature could be taken, e.g. previously known valid one). This issue has been patched in version 1.1.7.

Affected: npm: tiny-secp256k1

### Summary

Private key can be extracted on signing a malicious JSON-stringifiable object, when global Buffer is [`buffer` package](https://www.npmjs.com/package/buffer)

### Details

This affects only environments where `require('buffer')` is <https://npmjs.com/buffer> E.g.: browser bundles, React Native apps, etc.

`Buffer.isBuffer` check can be bypassed, resulting in `k` reuse for different messages, leading to private key extraction over a single invalid message (and a second one for which any message/signature could be taken, e.g. previously known valid one)

v2.x is unaffected as it verifies input to be an actual `Uint8Array` instance

Such a message can be constructed for any already known message/signature pair, meaning that the attack needs only a single malicious message being signed for a full key extraction

While signing unverified attacker-controlled messages would be problematic itself (and exploitation of this needs such a scenario), signing a single message still should not leak the private key

Also, message validation could have the same bug (out of scope for this report, but could be possible in some situations), which makes this attack more likely when used in a chain

https://github.com/bitcoinjs/tiny-secp256k1/pull/140 is a subtle fix for this

### PoC

This code deliberately doesn't provide `funnyBuffer` and `extractTiny` for now, could be updated later

```js import secp256k1 from 'tiny-secp256k1' import crypto from 'crypto'

const key = crypto.rand…