CVE-2025-6547: pbkdf2 Signature Spoofing Vulnerability

CVE-2025-6547 Overview

CVE-2025-6547 is a critical Improper Input Validation vulnerability affecting the pbkdf2 JavaScript library, a popular browserify-compatible implementation of the Password-Based Key Derivation Function 2. This vulnerability enables Signature Spoofing through improper validation of input types, potentially allowing attackers to bypass cryptographic protections in applications relying on this library for password hashing and key derivation operations.

The flaw resides in the to-buffer.js module, where insufficient type checking allows unexpected input types to be processed, potentially leading to signature validation bypasses in cryptographic workflows.

Critical Impact

Applications using pbkdf2 versions 3.1.2 and earlier are vulnerable to signature spoofing attacks that could undermine authentication mechanisms and cryptographic integrity checks.

Affected Products

• pbkdf2 versions <=3.1.2
• Applications using browserify/pbkdf2 for password hashing
• Node.js projects with pbkdf2 dependency

Discovery Timeline

• 2025-06-23 - CVE-2025-6547 published to NVD
• 2025-06-23 - Last updated in NVD database

Technical Details for CVE-2025-6547

Vulnerability Analysis

This vulnerability stems from inadequate input validation in the pbkdf2 library's buffer conversion routine. The to-buffer.js module is responsible for converting various input types (strings, Buffers, typed arrays) into a consistent Buffer format for cryptographic operations. Prior to the patch, the input type checking logic contained gaps that could allow improperly validated inputs to pass through the conversion process.

The weakness classified under CWE-20 (Improper Input Validation) manifests when the library fails to properly validate and sanitize input data before using it in cryptographic operations. This can lead to signature spoofing scenarios where an attacker crafts malicious input that bypasses validation checks, potentially compromising the integrity of derived keys or authentication tokens.

Root Cause

The root cause lies in the original to-buffer.js implementation which used a sequential type-checking approach that did not comprehensively handle all valid buffer-like types. The original code checked for Buffer.isBuffer(), string types, and ArrayBuffer.isView() separately, but the logic flow and type coercion could allow certain edge-case inputs to be processed incorrectly.

The patch introduces proper type validation using the to-buffer package and adds explicit checks for Uint8Array instances and proper ArrayBuffer.isView detection, ensuring all inputs are correctly validated before cryptographic processing.

Attack Vector

The attack vector is network-based, requiring no user interaction or privileges. An attacker could exploit this vulnerability by:

1. Crafting specially formed input data that exploits the type validation gaps
2. Submitting this malicious input to an application using the vulnerable pbkdf2 library
3. Bypassing signature validation to forge authentication tokens or compromise key derivation

The vulnerability requires certain preconditions to be met (reflected in the attack complexity), making exploitation non-trivial but still feasible in targeted attacks.

 'use strict';
 
 var Buffer = require('safe-buffer').Buffer;
+var toBuffer = require('to-buffer');
+
+var useUint8Array = typeof Uint8Array !== 'undefined';
+var useArrayBuffer = useUint8Array && typeof ArrayBuffer !== 'undefined';
+var isView = useArrayBuffer && ArrayBuffer.isView;
 
 module.exports = function (thing, encoding, name) {
-	if (Buffer.isBuffer(thing)) {
-		return thing;
-	}
-	if (typeof thing === 'string') {
-		return Buffer.from(thing, encoding);
-	}
-	if (ArrayBuffer.isView(thing)) {
-		return Buffer.from(thing.buffer);
+	if (
+		typeof thing === 'string'
+		|| Buffer.isBuffer(thing)
+		|| (useUint8Array && thing instanceof Uint8Array)
+		|| (isView && isView(thing))
+	) {
+		return toBuffer(thing, encoding);
 	}
-	throw new TypeError(name + ' must be a string, a Buffer, a typed array or a DataView');
+	throw new TypeError(name + ' must be a string, a Buffer, a Uint8Array, or a DataView');
 };

Source: GitHub Commit Changes

The patch demonstrates the security fix by introducing the to-buffer package for proper input normalization and adding comprehensive type checking with explicit Uint8Array and ArrayBuffer.isView validation before processing.

Detection Methods for CVE-2025-6547

Indicators of Compromise

• Unexpected authentication successes with invalid credentials in applications using pbkdf2
• Anomalous input types being passed to cryptographic functions in application logs
• Failed signature validations followed by unexpected bypasses

Detection Strategies

• Audit package.json and package-lock.json files for pbkdf2 versions <=3.1.2
• Implement software composition analysis (SCA) scanning in CI/CD pipelines to detect vulnerable dependencies
• Monitor application logs for unusual authentication patterns or cryptographic operation anomalies
• Use dependency scanning tools like npm audit or Snyk to identify vulnerable packages

Monitoring Recommendations

• Enable verbose logging for authentication and cryptographic operations in affected applications
• Monitor for unusual patterns in key derivation or password verification workflows
• Implement runtime application self-protection (RASP) to detect input validation bypass attempts
• Set up alerts for dependency vulnerability disclosures affecting npm packages

How to Mitigate CVE-2025-6547

Immediate Actions Required

• Update pbkdf2 to the latest patched version immediately
• Run npm audit to verify all instances of pbkdf2 in your dependency tree
• Review applications using pbkdf2 for potential exploitation indicators
• Regenerate any cryptographic keys or tokens that may have been derived using the vulnerable version

Patch Information

The vulnerability has been addressed by the maintainers. Apply the security patch by updating to the latest version of pbkdf2. Review the GitHub Security Advisory and the commit changes for technical details on the fix.

Workarounds

• If immediate patching is not possible, implement additional input validation before passing data to pbkdf2 functions
• Add explicit type checking to ensure only valid Buffer, string, Uint8Array, or DataView types are passed to cryptographic functions
• Consider temporarily switching to alternative PBKDF2 implementations while awaiting patch deployment

# Update pbkdf2 to the latest patched version
npm update pbkdf2

# Verify the installed version
npm list pbkdf2

# Run security audit to check for remaining vulnerabilities
npm audit