Summary
pbkdf2 silently disregards Uint8Array input, returning static keys
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
Uint8Arrayinput (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
The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2025-6547? CVE-2025-6547 is a critical-severity improper input validation vulnerability in pbkdf2 (npm), affecting versions >= 1.0.0, <= 3.1.2. It is fixed in 3.1.3. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
- Which versions of pbkdf2 are affected by CVE-2025-6547? pbkdf2 (npm) versions >= 1.0.0, <= 3.1.2 is affected.
- Is there a fix for CVE-2025-6547? Yes. CVE-2025-6547 is fixed in 3.1.3. Upgrade to this version or later.
- Is CVE-2025-6547 exploitable, and should I be worried? Whether CVE-2025-6547 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-6547 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2025-6547? Upgrade
pbkdf2to 3.1.3 or later.