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pbkdf2 returns predictable uninitialized/zero-filled memory for non-normalized or unimplemented algos

Critical severity GitHub Reviewed Published Jun 23, 2025 in browserify/pbkdf2 • Updated Jun 23, 2025

Package

npm pbkdf2 (npm)

Affected versions

>= 3.0.10, <= 3.1.2

Patched versions

3.1.3

Description

Summary

This affects both:

  1. Unsupported algos (e.g. sha3-256 / sha3-512 / sha512-256)
  2. Supported but non-normalized algos (e.g. Sha256 / Sha512 / SHA1 / sha-1 / sha-256 / sha-512)

All of those work correctly in Node.js, but this polyfill silently returns highly predictable ouput

Under Node.js (only with pbkdf2/browser import, unlikely) / Bun (pbkdf2 top-level import is affected), the memory is not zero-filled but is uninitialized, as Buffer.allocUnsafe is used

Under browsers, it just returns zero-filled buffers
(Which is also critical, those are completely unacceptable as kdf output and ruin security)

Were you affected?

The full list of arguments that were not affected were literal:

  • 'md5'
  • 'sha1'
  • 'sha224'
  • 'sha256'
  • 'sha384'
  • 'sha512'
  • 'rmd160'
  • 'ripemd160'

Any other arguments, e.g. representation variations of the above ones like 'SHA-1'/'sha-256'/'SHA512' or different algos like 'sha3-512'/'blake2b512', while supported on Node.js crypto module, returned predictable output on pbkdf2 (or crypto browser/bundlers polyfill)

Beware of packages re-exporting this under a different signature, like (abstract):

const crypto = require('crypto')
module.exports.deriveKey = (algo, pass, salt) => crypto.pbkdf2Sync(pass, salt, 2048, 64, algo)

In this case, the resulting deriveKey method is also affected (to the same extent / conditions as listed here).

Environments

This affects require('crypto') in polyfilled mode (e.g. from crypto-browserify, node-libs-browser, vite-plugin-node-polyfills, node-stdlib-browser, etc. -- basically everything that bundles/polfyills crypto

  • In bundled code (e.g. Webpack / Vite / whatever), this affects require('crypto') and require('pbkdf2')
  • On Node.js, this does not affect require('pbkdf2') (or require('crypto') obviously), but affects require('pbkdf2/browser')
  • On Bun, this does affect require('pbkdf2') and require('pbkdf2/browser') (and returns uninitialized memory, often zeros / sparse flipped bytes)

PoC

const node = require('crypto')
const polyfill = require('pbkdf2/browser')

const algos = [
  'sha3-512', 'sha3-256', 'SHA3-384',
  'Sha256', 'Sha512', 'sha512-256',
  'SHA1', 'sha-1',
  'blake2b512',
  'RMD160', 'RIPEMD-160', 'ripemd-160',
]
for (const algo of algos) {
  for (const { pbkdf2Sync } of [node, polyfill]) {
    const key = pbkdf2Sync('secret', 'salt', 100000, 64, algo)
    console.log(`${algo}: ${key.toString('hex')}`);
  }
}

Output (odd lines are Node.js, even is pbkdf2 module / polyfill):

sha3-512: de00370414a3251d6d620dc8f7c371644e5d7f365ab23b116298a23fa4077b39deab802dd61714847a5c7e9981704ffe009aee5bb40f6f0103fc60f3d4cedfb0
sha3-512: 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
sha3-256: 76bf06909b91e4c968700078ee36af92019d0839ab1fea2f345c6c8685074ca0179302633fbd84d22cff4f8744952b2d07edbfc9658e95d30fb4e93ee067c7c9
sha3-256: 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
SHA3-384: 2b2b41b73f9b7bcd023f709ea84ba3c29a88edc311b737856ba9e74a2d9a928f233eb8cb404a9ba93c276edf6380c692140024a0bc12b75bfa38626207915e01
SHA3-384: 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
Sha256: 3fa094211c0cf2ed1d332ab43adc69aab469f0e0f2cae6345c81bb874eef3f9eb2c629052ec272ca49c2ee95b33e7ba6377b2317cd0dacce92c4748d3c7a45f0
Sha256: 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
Sha512: 3745e482c6e0ade35da10139e797157f4a5da669dad7d5da88ef87e47471cc47ed941c7ad618e827304f083f8707f12b7cfdd5f489b782f10cc269e3c08d59ae
Sha512: 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
sha512-256: e423f61987413121418715d0ebf64cb646042ae9a09fe4fd2c764a4f186ba28cf70823fdc2b03dda67a0d977c6f0a0612e5ed74a11e6f32b033cb658fa9f270d
sha512-256: 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
SHA1: 0e24bc5a548b236e3eb3b22317ef805664a88747c725cd35bfb0db0e4ae5539e3ed5cd5ba8c0ac018deb6518059788c8fffbe624f614fbbe62ba6a6e174e4a72
SHA1: 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
sha-1: 0e24bc5a548b236e3eb3b22317ef805664a88747c725cd35bfb0db0e4ae5539e3ed5cd5ba8c0ac018deb6518059788c8fffbe624f614fbbe62ba6a6e174e4a72
sha-1: 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
blake2b512: d3d661100c5ffb79bdf3b5c77d1698e621414cba40e2348bd3f1b10fbd2fe97bff4dc7d76474955bfefa61179f2a37e9dddedced0e7e79ef9d8c678080d45926
blake2b512: 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
RMD160: ec65dbad1485616cf0426725d64e009ad3e1633543746ccb56b7f06eb7ce51d0249aaef27c879f32911a7c0accdc83389c2948ddec439114f6165366f9b4cca2
RMD160: 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
RIPEMD-160: ec65dbad1485616cf0426725d64e009ad3e1633543746ccb56b7f06eb7ce51d0249aaef27c879f32911a7c0accdc83389c2948ddec439114f6165366f9b4cca2
RIPEMD-160: 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
ripemd-160: ec65dbad1485616cf0426725d64e009ad3e1633543746ccb56b7f06eb7ce51d0249aaef27c879f32911a7c0accdc83389c2948ddec439114f6165366f9b4cca2
ripemd-160: 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

Uninitialized memory

const { pbkdf2Sync } = require('pbkdf2/browser') // or just 'pbkdf2' on Bun will do this too

let prev
for (let i = 0; i < 100000; i++) {
  const key = pbkdf2Sync('secret', 'salt', 100000, 64, 'sha3-256')
  const hex = key.toString('hex')
  if (hex !== prev) console.log(hex);
  prev = hex
}

Affected versions

Seems to be since browserify/pbkdf2@9699045

Impact

This is critical, browserifying code might silently generate zero-filled keys instead of proper ones, for code that was working on Node.js or in test environment

Just updating to a fixed version is not enough: if anyone was using pbkdf2 lib (e.g. via crypto-browserify or directly) on algos not from the literal string list (see "were you affected"), recheck where those keys went / how they were used, and take action accordingly

Note

Most likely, you receive this either through a subdep using pbkdf2 module directly (and then it is used), or through crypto-browserify (and the usage depends on whether you or any of your subdeps were calling pbkdf2/pbkdf2Sync methods from Node.js crypto inside your bundle)

When targeting non-Node.js, prever avoiding Node.js crypto polyfill at all, and use crypto.subtle and/or modern/audited cryptography primitives instead

References

@ljharb ljharb published to browserify/pbkdf2 Jun 23, 2025
Published by the National Vulnerability Database Jun 23, 2025
Published to the GitHub Advisory Database Jun 23, 2025
Reviewed Jun 23, 2025
Last updated Jun 23, 2025

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements Present
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality Low
Integrity High
Availability None
Subsequent System Impact Metrics
Confidentiality High
Integrity High
Availability High

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:H/VA:N/SC:H/SI:H/SA:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(25th percentile)

Weaknesses

CVE ID

CVE-2025-6545

GHSA ID

GHSA-h7cp-r72f-jxh6

Source code

Credits

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