CVE-2026-74899 in openssl_encrypt
Summary
by MITRE • 08/17/2026
openssl_encrypt versions before 1.4.0 contain a sandbox escape vulnerability in IsolatedPluginExecutor that exposes Python type objects in restricted exec() builtins. Attackers can traverse the Python class hierarchy via __class__.__mro__.__subclasses__() to access system functions and execute arbitrary OS commands.
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Analysis
by VulDB Data Team • 08/17/2026
The OpenSSL Encrypt library, specifically versions prior to 1.4.0, contains a critical sandbox escape vulnerability within its IsolatedPluginExecutor component. This flaw arises from an improper implementation of restricted execution environments for Python code plugins. The core issue lies in the exposure of sensitive Python type objects through the built-in functions available during isolated execution. While the intent was to create a secure boundary preventing arbitrary command execution, the actual implementation failed to adequately restrict access to fundamental object attributes that allow traversal of the class hierarchy. This oversight creates a significant security gap where untrusted code can break out of its intended sandbox constraints and interact with the underlying system environment in unauthorized ways.
The technical mechanism exploited by this vulnerability involves accessing internal Python objects through standard attribute lookups on built-in types. Specifically, attackers leverage the _class_ attribute to access the type object associated with a given instance. From there, they utilize the _mro_ (Method Resolution Order) tuple and the _subclasses_() method to enumerate all subclasses of that type. By iterating through these subclasses, an attacker can locate specific classes such as os.system or other functions capable of executing operating system commands. This technique effectively bypasses the restrictions imposed by the restricted exec() builtins because it does not rely on direct access to forbidden modules but rather constructs a path to them using allowed object introspection capabilities.
This vulnerability is classified under CWE-94, which describes Improper Control of Generation of Code (Code Injection), and more specifically relates to CWE-78, the improper neutralization of special elements used in an OS command (OS Command Injection). The attack vector aligns with MITRE ATT&CK technique T1059.006, representing Python code execution within a broader context of script interpreter abuse. The severity is high because it allows for remote or local arbitrary code execution depending on the context in which OpenSSL Encrypt processes untrusted input. Once an attacker gains access to system functions via this sandbox escape, they can execute any command available to the user running the application, leading to full compromise of the host system.
The operational impact of this vulnerability is severe, as it undermines the fundamental security model provided by isolated plugin execution. Applications relying on OpenSSL Encrypt for secure processing of untrusted data or plugins are at risk of complete system takeover if they do not upgrade immediately. Attackers can exfiltrate sensitive data, install malware, pivot to other systems within a network, or disrupt services by executing destructive commands. The ease with which this exploit can be constructed using standard Python features makes it particularly dangerous in environments where plugin-based architectures are common for extending functionality dynamically.
To mitigate this risk, organizations must upgrade OpenSSL Encrypt to version 1.4.0 or later immediately upon availability. This update addresses the sandbox escape by properly restricting access to internal object attributes and preventing traversal of the class hierarchy through _subclasses_. In addition to upgrading, administrators should implement strict input validation for any data passed into plugin execution contexts. It is also advisable to run applications with minimal privileges using principle of least privilege to limit the potential damage even if a sandbox escape occurs. Regular security audits and static code analysis tools configured to detect dangerous patterns like _subclasses_ usage in restricted environments can further reduce exposure to similar vulnerabilities in custom or third-party Python-based components.