The **Bleichenbacher Attack** is a sophisticated cryptographic attack that targets the RSA encryption scheme, specifically exploiting the RSA PKCS #1 v1.5 padding method. This attack takes advantage of vulnerabilities in systems that provide feedback on the validity of the padding used during the decryption process.

### How It Works:
The attack utilizes a *padding oracle*, which reveals whether the padding of an RSA-encrypted message is correct. By sending crafted ciphertexts to the oracle and analyzing the responses, an attacker can recover the plaintext message without needing access to the private key. This process typically involves the following steps:

1. **Crafting Ciphertext**: The attacker generates a series of modified ciphertexts based on the target ciphertext.
2. **Querying the Oracle**: Each modified ciphertext is sent to the application, which returns whether the decryption is valid (i.e., whether the padding is correct).
3. **Inferring Plaintext**: By systematically altering the ciphertext and observing the oracle's responses, the attacker can deduce the original plaintext.

### Risks of Not Addressing the Bleichenbacher Attack:
1. **Confidentiality Compromise**: Attackers can decrypt sensitive information, exposing confidential data such as personal and financial information.
2. **Data Integrity Issues**: An attacker can manipulate the ciphertext, leading to unauthorized changes to the data.
3. **Regulatory Compliance Violations**: Failure to secure against this attack can result in non-compliance with data protection regulations such as GDPR or HIPAA.

### Example Scenario:
Imagine an e-commerce website that encrypts sensitive user data, like payment information, using RSA PKCS #1 v1.5 padding. If an attacker can interact with the site and leverage the Bleichenbacher Attack, they may successfully decrypt this sensitive data, potentially leading to financial fraud or identity theft.