CVE-2025-6547

Summary

On historic but declared as supported Node.js versions (0.12-2.x), pbkdf2 silently disregards Uint8Array input

This only affects Node.js <3.0.0, but pbkdf2 claims to:

• Support Node.js >= 0.12 (and there seems to be ongoing effort in this repo to maintain that)
• Support Uint8Array input (input is typechecked against Uint8Array, and the error message includes e.g. "Password must be a string, a Buffer, a typed array or a DataView"

Details

The error is in toBuffer method

This vulnerability somehow even made it to tests: https://github.com/browserify/pbkdf2/commit/eb9f97a66ed83836bebc4ff563a1588248708501

There, resultsOld (where mismatch results) are just invalid output generated from empty password/salt instead of the supplied one

PoC

On Node.js/io.js < 3.0.0

> require('pbkdf2').pbkdf2Sync(new Uint8Array([1,2,3]), new Uint8Array([1,3,4]), 1024, 32, 'sha256')
<Buffer 21 53 cd 5b a5 f0 15 39 2f 68 e2 40 8b 21 ba ca 0e dc 7b 20 d5 45 a4 8a ea b5 95 9f f0 be bf 66>
// But that's just a hash of empty data with empty password:
> require('pbkdf2').pbkdf2Sync('', '', 1024, 32, 'sha256')
<Buffer 21 53 cd 5b a5 f0 15 39 2f 68 e2 40 8b 21 ba ca 0e dc 7b 20 d5 45 a4 8a ea b5 95 9f f0 be bf 66>
// Node.js crypto is fine even on that version:
> require('crypto').pbkdf2Sync(new Uint8Array([1,2,3]), new Uint8Array([1,3,4]), 1024, 32, 'sha256')
<Buffer 78 10 cc 84 b7 bb 85 cd c8 37 ca 68 da a9 4c 33 db ae c2 3d 5b d4 95 76 da 33 f9 95 ac 51 f4 45>
// Empty hash from Node.js, for comparison
> require('crypto').pbkdf2Sync('', '', 1024, 32, 'sha256')
<Buffer 21 53 cd 5b a5 f0 15 39 2f 68 e2 40 8b 21 ba ca 0e dc 7b 20 d5 45 a4 8a ea b5 95 9f f0 be bf 66>

Impact

Static hashes being outputted and used as keys/passwords can completely undermine security

That said, no one should be using those Node.js versions anywhere now, so I would recommend to just drop them

This lib should not pretend to work on those versions while outputting static data though

Just updating to a fixed version is not enough: if anyone was using pbkdf2 lib (do not confuse with Node.js crypto.pbkdf2) or anything depending on it with Node.js/io.js < 3.0.0, recheck where those keys went / how they were used,  and take action accordingly