CVE-2026-74889 in openssl_encrypt
Summary
by MITRE • 08/17/2026
openssl_encrypt versions before 1.4.0 use HKDF with no salt and static info parameter in key normalization functions, reducing entropy extraction and determinism. Attackers can exploit predictable key derivation with identical inputs to weaken cryptographic security against multi-target attacks.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 08/17/2026
The vulnerability identified in OpenSSL Encrypt prior to version 1.4.0 centers on a critical implementation flaw within the key normalization functions that utilize the HMAC-based Key Derivation Function, commonly known as HKDF. In secure cryptographic practice, HKDF is designed to extract and expand keys from input secret material while ensuring high entropy through the use of random salts and unique info parameters. However, in these affected versions, the library implements HKDF with a null or empty salt value and employs static, unchanging info parameters during key derivation processes. This configuration fundamentally undermines the security properties that HKDF is intended to provide, specifically regarding randomness and uniqueness across different encryption sessions or contexts.
From a technical perspective, the absence of a random salt means that the initial extraction phase does not introduce additional entropy derived from unpredictable data. Furthermore, using static info parameters ensures that for any given input keying material, the resulting derived keys will be identical every time they are generated under similar conditions. This determinism creates a predictable pattern in cryptographic outputs where multiple users or systems relying on this library may derive the same session keys if their underlying secret materials share similarities or are subjected to known inputs. The lack of salt effectively removes one layer of defense against precomputation attacks and reduces the complexity required for an adversary to reverse-engineer derived secrets from observed ciphertexts.
The operational impact of this flaw is significant, particularly in environments where multi-target attacks are a concern. When cryptographic keys are deterministically generated without sufficient randomness, attackers can exploit these predictable derivations to weaken overall security posture. Specifically, if multiple targets use the same or related input materials with identical static parameters, an attacker who compromises one target may gain insights that facilitate breaking encryption for other targets using similar configurations. This scenario is particularly dangerous in large-scale deployments such as cloud services, IoT networks, or enterprise communication systems where shared secrets might be reused across different instances due to misconfiguration or default settings provided by the library.
This vulnerability aligns with CWE-328, which classifies the use of weak cryptographic algorithms, and more specifically relates to issues surrounding insufficient randomness in key generation processes often categorized under CWE-330 regarding failure to generate random numbers properly for security purposes. In terms of offensive cybersecurity frameworks like MITRE ATT&CK, this flaw could be leveraged during techniques involving credential access or defense evasion by allowing adversaries to perform cryptanalysis more efficiently than intended against multiple endpoints simultaneously. The predictability reduces the computational cost required for brute-force attempts and enables targeted attacks that exploit structural weaknesses in key derivation logic rather than relying solely on raw computing power.
To mitigate this risk, organizations must upgrade immediately to OpenSSL Encrypt version 1.4.0 or later where these implementation details have been corrected to ensure proper entropy injection via random salts and dynamic info parameters. Until the update is applied, administrators should review application code that interacts with key normalization functions to manually inject high-entropy salt values derived from secure random number generators such as /dev/urandom on Unix-like systems or BCryptGenRandom on Windows platforms. Additionally, it is crucial to audit configurations for any hardcoded static info strings and replace them with unique identifiers tied to specific sessions, users, or contexts to ensure that each key derivation operation produces distinct outputs even when input materials are similar. Regular security audits focusing on cryptographic implementation details remain essential to prevent such subtle but impactful vulnerabilities from compromising sensitive data in production environments.