CVE-2018-15560 in PyCryptodome
Summary
by MITRE
PyCryptodome before 3.6.6 has an integer overflow in the data_len variable in AESNI.c, related to the AESNI_encrypt and AESNI_decrypt functions, leading to the mishandling of messages shorter than 16 bytes.
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Analysis
by VulDB Data Team • 05/02/2023
The vulnerability identified as CVE-2018-15560 represents a critical integer overflow flaw within the PyCryptodome cryptographic library version 3.6.5 and earlier. This issue manifests in the AESNI.c source file where the data_len variable experiences an integer overflow during encryption and decryption operations. The flaw specifically impacts the AESNI_encrypt and AESNI_decrypt functions that leverage Advanced Encryption Standard New Instructions for hardware-accelerated AES operations on compatible processors. When processing messages shorter than 16 bytes, the library fails to properly handle the length parameter, creating a scenario where the integer overflow can lead to unexpected behavior in the cryptographic operations.
The technical exploitation of this vulnerability occurs through the manipulation of input data lengths that trigger the integer overflow condition in the data_len variable. This overflow results in incorrect calculation of message boundaries and can cause the cryptographic functions to process data incorrectly, potentially leading to data corruption or unauthorized access to plaintext information. The issue stems from inadequate bounds checking and overflow protection mechanisms within the cryptographic implementation, particularly when dealing with small data payloads that fall below the standard AES block size of 16 bytes. This type of vulnerability falls under the CWE-190 category of Integer Overflow or Wraparound, which is a well-documented weakness in cryptographic implementations that can severely compromise security guarantees.
The operational impact of this vulnerability extends beyond simple data corruption, as it can enable attackers to potentially extract sensitive information through carefully crafted inputs that exploit the overflow condition. When cryptographic libraries fail to properly validate input parameters, especially those related to data length, the security of encrypted communications becomes compromised. The vulnerability affects systems that rely on PyCryptodome for AES encryption and decryption operations, particularly those using hardware acceleration features. Attackers could potentially leverage this flaw to perform side-channel attacks or manipulate the encryption process to gain unauthorized access to data, making this issue particularly dangerous in environments where cryptographic security is paramount.
Mitigation strategies for CVE-2018-15560 require immediate upgrading of the PyCryptodome library to version 3.6.6 or later, where the integer overflow has been properly addressed through enhanced input validation and overflow protection mechanisms. Organizations should also implement comprehensive testing procedures to verify that cryptographic operations handle edge cases correctly, particularly for messages of varying lengths. The fix typically involves implementing proper bounds checking and ensuring that integer variables cannot overflow during length calculations. Additionally, security teams should monitor for similar vulnerabilities in other cryptographic libraries and maintain updated security patches for all cryptographic components within their infrastructure, following the ATT&CK framework's guidance on software supply chain security and cryptographic vulnerabilities.