CBC (Cipher Block Chaining) mode has several vulnerabilities that can be exploited if not implemented correctly. Some of the key vulnerabilities include:
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Padding Oracle Attack: If an application reveals whether the padding of a decrypted message is correct or not, an attacker can exploit this information to decrypt ciphertexts without knowing the key. This is done by sending modified ciphertexts and observing the application's responses.
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Bit Flipping Attack: An attacker can modify specific bits in the ciphertext, which will affect the corresponding bits in the plaintext after decryption. This can be used to manipulate the data being transmitted, such as changing a transaction amount in a financial application.
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IV Reuse: If the same IV is used for multiple encryption sessions with the same key, it can lead to vulnerabilities. An attacker can analyze the ciphertexts to find patterns and potentially recover the plaintext.
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Malicious IV Injection: If an attacker can control the IV, they may be able to manipulate the decryption process, leading to unauthorized access or data manipulation.
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Replay Attacks: An attacker can capture and resend valid ciphertexts to perform unauthorized actions, especially in scenarios where the application does not implement proper session management or nonce handling.
To mitigate these vulnerabilities, it is essential to use secure practices such as employing unique and random IVs for each encryption, validating input data, and implementing proper error handling to avoid leaking information about the encryption process.
