CVE-2026-81701 in openssl_encrypt
Summary
by MITRE • 08/27/2026
openssl_encrypt versions before 1.4.9 use a denylist to identify trusted built-in plugins, allowing unsigned plugins in top-level plugins/ directories and unknown subdirectories to bypass signature verification. Attackers can place malicious unsigned plugins following documented installation paths to achieve arbitrary code execution in the CLI process with access to passwords and cryptographic keys.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 08/27/2026
The vulnerability identified in OpenSSL Encrypt versions prior to 1.4.9 represents a critical flaw in the plugin loading mechanism, specifically stemming from an insufficient validation strategy for third-party extensions. The core technical issue lies in the use of a denylist approach rather than a strict allowlist when identifying trusted built-in plugins. A denylist operates by blocking known malicious patterns or paths while permitting everything else that does not match those specific exclusions. This architectural decision creates a significant security gap because it assumes that any plugin located outside explicitly blocked directories is safe to load, regardless of its origin or integrity status. Consequently, the system fails to enforce cryptographic signature verification for plugins residing in top-level plugins/ directories and various unknown subdirectories within the application structure.
This design flaw allows attackers to bypass the intended security controls by placing malicious unsigned plugins into these accessible locations. Since the software does not verify the digital signatures of plugins found in these specific paths, it proceeds to load them as if they were legitimate, trusted components. The operational impact is severe, granting an attacker arbitrary code execution within the command-line interface process that hosts OpenSSL Encrypt. This level of access effectively compromises the integrity and confidentiality of the entire system environment where the application runs.
The consequences of this compromise are particularly acute given the nature of cryptographic tools. An adversary with arbitrary code execution capabilities can intercept sensitive data processed by the tool, including plaintext passwords and private cryptographic keys stored in memory or passed as arguments. This exposure undermines the fundamental purpose of using encryption software, which is to protect data confidentiality and integrity. The attacker could potentially exfiltrate these credentials to external servers, use them for further lateral movement within a network, or decrypt previously secured communications and files that rely on those compromised keys.
From an industry standards perspective, this vulnerability aligns with CWE-20 Improper Input Validation, as the application fails to adequately validate the source and integrity of input components before processing them. It also relates closely to CWE-862 Missing Authorization, since the system does not properly enforce access control policies regarding which plugins are permitted to execute based on their trustworthiness. In terms of the MITRE ATT&CK framework, this exploit maps to T1059 Command and Scripting Interpreter for initial code execution via the CLI process and potentially T1553 Subvert Trust Controls if the attacker modifies system configurations to maintain persistence or evade detection.
Mitigation strategies must prioritize moving away from denylist-based validation models toward strict allowlisting mechanisms that explicitly define which plugins are authorized for loading based on verified digital signatures. Organizations should immediately upgrade OpenSSL Encrypt to version 1.4.9 or later, where this logic has been corrected to enforce signature verification across all plugin directories regardless of their location within the file system structure. In environments where upgrading is not immediately feasible, administrators can implement compensating controls by restricting write access to the plugins/ directory and its subdirectories for non-privileged users, thereby preventing attackers from placing malicious unsigned code in these locations. Additionally, enabling strict logging for plugin loading events can aid in detecting attempts to load unauthorized components before they result in full system compromise.