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CVE-2025-6545

CVE-2025-6545: pbkdf2 returns predictable uninitialized/zero-filled memory for non-normalized or unimplemented algos

Summary

This affects both:

Unsupported algos (e.g. sha3-256 / sha3-512 / sha512-256)
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)

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CVE-2025-6545

CVE-2025-6545:

N/A

CVSS Score

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
pbkdf2	npm	>= 3.0.10, <= 3.1.2	3.1.3

Technical Details

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Root Cause Analysis

The vulnerability exists in the pbkdf2 package, where the key derivation functions pbkdf2 and pbkdf2Sync can return predictable (zero-filled or uninitialized) buffers instead of cryptographically secure keys. This issue was introduced in commit 9699045c37a07f8319cfb8d44e2ff4252d7a7078.

The root cause is the replacement of the robust create-hmac library with a new, internal HMAC implementation. This new implementation, found in lib/sync.js, uses a hardcoded map of lowercase algorithm names (md5, sha1, sha256, etc.) to determine the hash output size.

When a developer provides an algorithm name that is not in this exact list—either a non-normalized form like 'SHA256' (with uppercase letters) or a different but valid algorithm like 'sha3-512'—the internal logic fails to find the corresponding size. Instead of throwing an error, the code proceeds with incorrect parameters, ultimately leading to the generation of an insecure, predictable output.

This is a critical vulnerability because it can lead to systems generating and using weak or empty keys for sensitive operations, completely undermining the security of the key derivation process. The issue is particularly insidious because it fails silently, giving no indication that the generated key is insecure.

Vulnerable functions

Only Mi**o us*rs **n s** t*is s**tion

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WAF Protection Rules

WAF Rule

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Reasoning

*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.

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

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Basic Information

Basic Information

Concerned about an active attack path?

CVE-2025-6545: pbkdf2 returns predictable uninitialized/zero-filled memory for non-normalized or unimplemented algos

Summary

Were you affected?

CVE-2025-6545:

N/A

-

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Technical Details

Technical Details

Vulnerability IntelligenceMiggo AI

Root Cause Analysis

Vulnerable functions

Vulnerability IntelligenceMiggo AI

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WAF Protection Rules

WAF Rule

Reasoning

Basic Information

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Root Cause Analysis

Vulnerable functions

Technical Details

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CVE-2025-6545: pbkdf2 returns predictable uninitialized/zero-filled memory for non-normalized or unimplemented algos

Summary

Were you affected?

Environments

PoC

Uninitialized memory

Affected versions

Impact

Note

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