CVE-2026-81716 in openssl_encrypt
Summary
by MITRE • 08/27/2026
openssl_encrypt (pip: openssl-encrypt) versions before 1.4.9 contain a path traversal flaw in PluginSandbox._is_safe_path, which authorized file access using a bare string-prefix match. A sandboxed plugin without the READ_FILES permission could read or write another plugin's directory that merely shares a name prefix (e.g., .../plugins/foobar matching allowed .../plugins/foo), breaking per-plugin isolation within the same user. Fixed by matching each allowed directory exactly or with a trailing path separator.
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Analysis
by VulDB Data Team • 08/27/2026
The vulnerability identified in openssl-encrypt versions prior to 1.4.9 represents a critical failure in access control logic, specifically manifesting as a path traversal flaw within the PluginSandbox._is_safe_path function. This component is responsible for validating file paths to ensure that sandboxed plugins operate strictly within their designated boundaries. The core technical deficiency lies in the implementation of the security check, which relied on a naive string-prefix matching algorithm rather than robust canonicalization or exact directory verification. By simply checking if a requested path begins with an allowed prefix, such as verifying that /plugins/foobar starts with /plugins/foo, the system failed to account for hierarchical file system structures where one directory name is merely a substring of another. This logical error allows malicious actors to bypass isolation mechanisms intended to separate plugin environments within the same user context.
From a technical perspective, this flaw aligns closely with CWE-22: Improper Limitation of a Pathname to a Restricted Directory and CWE-732: Incorrect Permission Assignment for Critical Resource. The vulnerability enables unauthorized read or write operations against directories belonging to other plugins that share a common name prefix. For instance, if Plugin A is restricted to the /plugins/foo directory, an attacker controlling a plugin with access permissions could craft requests targeting paths like /plugins/foobar/badfile.txt. Because foobar starts with foo, the flawed validation logic would erroneously permit this access. This breaks the fundamental principle of per-plugin isolation, effectively allowing one compromised or maliciously crafted plugin to exfiltrate sensitive data from another plugin's storage space or inject arbitrary files that could be executed by other components sharing similar naming conventions.
The operational impact of this vulnerability is significant for any deployment relying on openssl-encrypt plugins within a shared user environment. An attacker who has achieved code execution in a sandboxed plugin with limited permissions can leverage this flaw to escalate privileges and access resources outside their intended scope. This could lead to the disclosure of confidential information, such as cryptographic keys or user data stored by other plugins, or facilitate further attacks through file injection if write permissions are inadvertently granted. The lack of strict boundary enforcement undermines the trust model of the plugin architecture, potentially leading to a complete compromise of the application's security posture even when individual plugins appear secure in isolation.
To mitigate this vulnerability, it is essential to upgrade openssl-encrypt to version 1.4.9 or later, where the path validation logic has been corrected. The fix involves replacing the simple string-prefix match with a more rigorous check that ensures each allowed directory matches exactly or includes a trailing path separator. This approach prevents substring collisions by ensuring that /plugins/foo does not inadvertently grant access to /plugins/foobar. Additionally, developers should implement defense-in-depth strategies such as canonicalizing all file paths before validation and utilizing operating system-level security controls like chroot jails or SELinux contexts where possible. Regular auditing of permission assignments against CWE-732 guidelines will help prevent similar misconfigurations in future development cycles.
In terms of threat modeling, this vulnerability can be mapped to MITRE ATT&CK techniques related to unauthorized access and lateral movement within a host environment. Specifically, it relates to T1083: File and Directory Discovery, as the attacker uses the flaw to enumerate and access restricted directories. The exploitation path demonstrates how logical flaws in application-level security controls can undermine system-level isolation mechanisms. Security teams should prioritize patching this vulnerability immediately if they are running affected versions of openssl-encrypt, particularly in multi-tenant or plugin-based architectures where strict separation of duties is required for compliance with standards such as OWASP Application Security Verification Standard regarding input validation and access control enforcement.