PBKDF2 Hash (Django / passlib format) Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching pbkdf2 hash (django / passlib format), ported and verified for Python. In security-sensitive code, using an unverified regex can open the door to both false positives and denial-of-service attacks. The snippet below is ready to drop into your Python project — whether you're validating in a Django view, a FastAPI endpoint, or a standalone data processing script.

Python Implementation

# PBKDF2 Hash (Django / passlib format)
# ReDoS-safe | RegexVault — Security > Password Formats

import re

pbkdf2_hash_django_passlib_format_pattern = re.compile(r'^pbkdf2_sha(256|512)\$([0-9]+)\$([A-Za-z0-9+/=]{1,32})\$([A-Za-z0-9+/=]{43,86})$')

def validate_pbkdf2_hash_django_passlib_format(value: str) -> bool:
    return bool(pbkdf2_hash_django_passlib_format_pattern.fullmatch(value))

# Example
print(validate_pbkdf2_hash_django_passlib_format("pbkdf2_sha256$390000$abcdefghijklmnop$abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMN01234567890="))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Security > Password Formats category and carries a ReDoS-safe certification. That matters for Python developers because particularly important in Python web servers where CPU-bound regex operations can stall concurrent request handling. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Format: algorithm + $ + iterations + $ + salt (base64) + $ + hash (base64). Django default uses sha256 with 390000 iterations (Django 4.2). NIST SP 800-63b recommends at least 10000 iterations — modern systems should use much higher. SHA-512 is preferred over SHA-256.