vBulletin ≥ v3.8.5 Hash

What is vBulletin ≥ v3.8.5?

The vBulletin password hashing scheme (introduced in versions ≥ v3.8.5) is a legacy cryptographic format derived from PHP’s `crypt()` function with a custom salt prefix, designed to store user credentials in a MySQL database. Structurally, it follows a **MD5-based** hashing pipeline: the input password is first concatenated with a **static salt prefix** (`$vb[version]`) followed by a **random 8-character hexadecimal salt**, then hashed via MD5 twice—once with the raw salted input and again with the intermediate hash appended to the salt. The final output is a **32-character hexadecimal string** (e.g., `$vb123$1a2b3c4d5e6f7890$abcdef1234567890abcdef1234567890`), where the first segment (`$vb123$`) denotes the version, the middle (`1a2b3c4d5e6f7890`) is the salt, and the remainder is the double-hashed result. This scheme was primarily used to store passwords in vBulletin forums, though its reliance on MD5 and predictable salt patterns rendered it insecure by modern standards.

The vulnerability of this format stems from its **fundamental cryptographic flaws**, primarily the use of **MD5**, a collision-prone hash function with known preimage and rainbow table attacks. The **lack of a unique salt per user** (only the 8-character hex segment varies) enables offline brute-force attacks via rainbow tables or dictionary attacks, as the same salted hashes can be precomputed for common passwords. Additionally, MD5’s **low collision resistance** allows attackers to craft custom inputs that produce identical hashes, facilitating **birthday attack** scenarios. The **double-hashing process** provides marginal security but is easily optimized on modern hardware—GPUs and FPGAs can compute millions of MD5 hashes per second, reducing cracking time to minutes for weak passwords. The **predictable salt prefix** (`$vb[version]`) further weakens entropy, as attackers can narrow down the search space by focusing on this pattern. These flaws collectively render the scheme **completely unsuitable for modern security requirements**, with tools like **Hashcat** or **John the Ripper** capable of cracking it efficiently.

Identifying vBulletin ≥ v3.8.5 Hashes

Identifying a hash blindly is often difficult because multiple algorithms can output strings of the exact same length. For example, a standard 32-character hexadecimal string could be MD5, NTLM, MD4, or LM. To definitively identify vBulletin ≥ v3.8.5, security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack vBulletin ≥ v3.8.5

If you need to recover the plaintext password for a vBulletin ≥ v3.8.5 hash during a penetration test or forensics investigation, you must supply the correct module ID to your cracking software. Use the exact commands provided at the top of this page to target the hash successfully.