CVE-2026-81719 in openssl_encrypt
Summary
by MITRE • 08/27/2026
openssl_encrypt before 1.4.9 executes untrusted third-party plugins with insufficient controls: the plugin signature policy defaulted to WARN, so an unsigned/unverifiable non-built-in plugin was compiled and executed in the host process at import time, before the runtime sandbox is installed. The only default gate was an incomplete, bypassable AST denylist. If a user is induced to load an attacker's plugin, this results in arbitrary code execution with the privileges of the user running openssl_encrypt. Fixed in 1.4.9 by defaulting the signature policy to ENFORCE for non-built-in plugins.
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Analysis
by VulDB Data Team • 08/27/2026
The vulnerability identified involves a critical flaw in the plugin loading mechanism within versions of openssl_encrypt prior to release 1.4.9, specifically concerning how untrusted third-party extensions are handled during initialization. The core issue stems from an insecure default configuration where the signature verification policy was set to WARN rather than ENFORCE for non-built-in plugins. This misconfiguration meant that when a user loaded a plugin authored by a third party, the system would not strictly validate its cryptographic signature or authenticity before proceeding with execution. Instead of rejecting unsigned or unverifiable code outright, the application merely issued a warning and continued processing, effectively trusting unverified input from external sources without sufficient validation controls in place.
From a technical perspective, this flaw allows for arbitrary code execution within the host process context because the plugin is compiled and executed at import time, which occurs before the runtime sandbox environment is fully established or enforced. The security boundary intended to isolate potentially malicious code was therefore bypassed entirely during this early initialization phase. The only protective measure in place was an incomplete Abstract Syntax Tree denylist designed to block specific known bad patterns. However, such static analysis-based filters are inherently limited and easily circumvented by attackers who can craft obfuscated or novel payloads that do not trigger the predefined denial rules but still achieve arbitrary execution capabilities. This represents a classic case of relying on insufficient access control mechanisms rather than strict cryptographic verification for plugin integrity.
The operational impact of this vulnerability is severe, as it leads to full compromise of the user account running openssl_encrypt if they are induced to load an attacker-controlled plugin. Since the code executes with the privileges of the invoking user, an attacker can escalate their influence within the system depending on those permissions. This could lead to data exfiltration, persistence mechanisms being installed, or further lateral movement across networked systems where such tools are deployed. The risk is particularly acute in environments where users may be tricked into installing malicious extensions through social engineering or compromised repositories, as there was no automatic enforcement of trust boundaries for external code modules during the critical startup sequence.
This vulnerability aligns with CWE-284 Improper Access Control and CWE-95 improper neutralization of direct system command elements, reflecting a failure to enforce proper security policies on executable content from untrusted sources. In terms of adversary tactics, it maps closely to ATT&CK technique T1059 Command and Scripting Interpreter, where attackers leverage legitimate software features for malicious purposes, as well as T1204 User Execution, which describes how users are tricked into running malicious code. The lack of sandbox enforcement at the time of plugin loading also relates to CWE-676 Use of Potentially Dangerous Function, highlighting the danger of executing unverified dynamic content in a privileged context without adequate isolation.
The issue was resolved in version 1.4.9 by changing the default signature policy for non-built-in plugins from WARN to ENFORCE. This change ensures that any plugin lacking a valid cryptographic signature or verifiable origin is rejected immediately rather than being executed with only a warning. By enforcing strict authentication and integrity checks before allowing code execution, the application establishes a stronger trust boundary between trusted built-in components and untrusted third-party extensions. Organizations using affected versions should upgrade to 1.4.9 or later as soon as possible. Additionally, administrators should audit their plugin repositories for any unsigned modules currently in use and implement strict whitelisting policies that only allow plugins from verified publishers to be loaded, thereby mitigating the risk of similar exploitation vectors in future deployments.