CVE-2020-7069 in PHP
Summary
by MITRE • 10/04/2020
In PHP versions 7.2.x below 7.2.34, 7.3.x below 7.3.23 and 7.4.x below 7.4.11, when AES-CCM mode is used with openssl_encrypt() function with 12 bytes IV, only first 7 bytes of the IV is actually used. This can lead to both decreased security and incorrect encryption data.
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Analysis
by VulDB Data Team • 11/16/2020
The vulnerability identified as CVE-2020-7069 represents a critical cryptographic flaw in PHP's OpenSSL extension that affects multiple version branches including 7.2.x below 7.2.34, 7.3.x below 7.3.23, and 7.4.x below 7.4.11. This issue specifically impacts the Advanced Encryption Standard in Counter with Cipher Block Chaining Message Authentication Code mode, commonly known as AES-CCM encryption. The flaw manifests when developers utilize the openssl_encrypt() function with a 12-byte initialization vector, creating a significant security gap that undermines the intended cryptographic protection.
The technical root cause of this vulnerability lies in the improper handling of initialization vectors within the AES-CCM implementation. When PHP processes encryption operations using this mode with a 12-byte IV, the system only effectively utilizes the first 7 bytes of the provided initialization vector while ignoring the remaining 5 bytes. This partial utilization creates a substantial reduction in the entropy and uniqueness of the encryption process, effectively weakening the cryptographic strength of the encrypted data. The vulnerability maps to CWE-327, which addresses the use of weak cryptographic algorithms and improper implementation of cryptographic functions, and aligns with ATT&CK technique T1552.001 related to unsecured credentials and data encryption.
The operational impact of this vulnerability extends beyond simple cryptographic weakness to encompass potential data integrity and confidentiality breaches. Attackers who can exploit this flaw may be able to perform partial decryption attacks or reduce the effective key space of the encryption, making brute force attacks more feasible. The reduced security margin created by this vulnerability compromises the assurance that data encrypted using AES-CCM mode maintains its confidentiality and integrity. Additionally, the improper handling of the IV can lead to incorrect encryption data behavior, where identical plaintexts might produce different ciphertexts or where the encryption process fails to properly incorporate the full initialization vector, resulting in potential data corruption or misinterpretation.
Organizations utilizing affected PHP versions should prioritize immediate patching to address this vulnerability, as the security implications extend to any applications that rely on AES-CCM encryption through the openssl_encrypt() function. The recommended mitigation strategy involves upgrading to the patched versions of PHP where the IV handling has been corrected to properly utilize all 12 bytes of the initialization vector. System administrators should also conduct thorough audits of applications that employ OpenSSL encryption functions to identify potential exposure and implement additional security controls where patching is not immediately feasible. Security teams should monitor for any anomalous encryption behaviors or data integrity issues that might indicate exploitation attempts against this vulnerability, particularly in environments where sensitive data is processed using AES-CCM mode with 12-byte IVs.