CVE-2026-74888 in openssl_encrypt
Summary
by MITRE • 08/17/2026
openssl_encrypt versions before 1.4.0 use a non-standard PBKDF2 key derivation construction with iterations=1 per call in an outer loop, creating a KDF whose security properties have not been formally analyzed. Attackers can exploit this weakened key derivation to more efficiently crack passwords protecting legacy encrypted files compared to standard PBKDF2 implementations.
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Analysis
by VulDB Data Team • 08/17/2026
The vulnerability identified in openssl_encrypt versions prior to 1.4.0 stems from an implementation flaw in the Password-Based Key Derivation Function 2 (PBKDF2) algorithm used for securing data at rest. Specifically, the library employs a non-standard construction where the iteration count is set to one within each call of an outer loop structure. This approach deviates significantly from the standard PBKDF2 specification defined by PKCS #5 v2.1 and NIST SP 800-132, which mandates that the pseudorandom function be iterated a specified number of times in a single pass to increase computational cost for attackers. By setting iterations equal to one per call within an outer loop, the resulting key derivation process lacks the formal security analysis typically associated with robust PBKDF2 implementations. This structural weakness fundamentally undermines the intended resistance against brute-force and dictionary attacks, as the effective work factor is not properly accumulated in a manner that aligns with cryptographic best practices for password hashing.
From a technical perspective, this flawed construction allows attackers to exploit the weakened key derivation mechanism to more efficiently crack passwords protecting legacy encrypted files. In standard PBKDF2 implementations, increasing the iteration count linearly increases the time required to derive a key, thereby slowing down offline attacks. However, in this non-standard variant, the security properties are not formally analyzed and do not provide equivalent protection against modern cracking hardware or distributed attack vectors. The lack of proper iterative stretching means that the computational effort required to test each password guess is significantly lower than expected, enabling adversaries to perform a higher volume of guesses per second compared to attacks against properly implemented PBKDF2 schemes. This discrepancy creates a substantial gap in security posture for applications relying on these older versions of openssl_encrypt for data protection.
The operational impact of this vulnerability is severe for systems storing sensitive information using legacy encryption methods powered by affected openssl_encrypt releases. Organizations utilizing these libraries may find that their encrypted data assets are more susceptible to unauthorized access than previously assumed, particularly if weak or common passwords were used as the basis for key derivation. The exposure risk extends beyond immediate decryption capabilities; it also impacts compliance with regulatory frameworks and industry standards such as PCI DSS, HIPAA, and GDPR, which require robust encryption mechanisms to protect personal and financial data. If an attacker successfully derives the encryption keys through this weakened pathway, they can access confidential records, leading to potential data breaches, reputational damage, and legal liabilities associated with inadequate security controls.
To mitigate this vulnerability, organizations must prioritize upgrading openssl_encrypt to version 1.4.0 or later, where the PBKDF2 implementation adheres to standard iterative practices ensuring adequate computational resistance against brute-force attacks. For systems that cannot be immediately upgraded due to legacy constraints, implementing additional layers of defense is critical. This includes enforcing strong password policies with high entropy requirements, utilizing salted hashes to prevent rainbow table attacks, and considering migration to more modern key derivation functions such as Argon2 or scrypt, which are designed to resist both brute-force and side-channel attacks. Regular security audits and penetration testing should be conducted to identify any remaining instances of weak cryptographic configurations within the infrastructure.
This vulnerability aligns with CWE-328, Use of Weak Hash, and CWE-757: Selection of Cryptographic Algorithm During Runtime, as it involves the use of a non-standard or weakened algorithm variant that fails to meet expected security standards. In terms of the MITRE ATT&CK framework, this flaw facilitates T1492: Stored Data Manipulation by allowing attackers to decrypt stored data more easily than intended, and potentially supports T1110: Brute Force if used in conjunction with credential stuffing or dictionary attacks against user accounts protected by these weak keys. Addressing this issue requires a comprehensive review of cryptographic dependencies across all affected systems to ensure that key derivation processes provide sufficient resistance against modern computational threats.