CVE-2026-74883 in openssl_encrypt
Summary
by MITRE • 08/17/2026
openssl_encrypt versions before 1.4.0 contain a sandbox bypass vulnerability where the plugin sandbox fails to restrict alternative file access methods like pathlib.Path and io.open. Attackers can import pathlib or io modules to read and write arbitrary files, completely bypassing the restricted_open file access controls.
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Analysis
by VulDB Data Team • 08/17/2026
The openssl_encrypt Python package prior to version 1.4.0 suffers from a critical sandbox escape vulnerability that undermines the intended security boundaries of its execution environment. This flaw stems from an incomplete implementation of input validation and resource isolation within the plugin system. While the developers implemented restricted_open controls to limit file access, they failed to account for alternative Python standard library modules capable of performing low-level operating system interactions. Specifically, the sandbox did not restrict imports or usage of pathlib.Path and io.open, which provide direct pathways to interact with the host filesystem outside the scope of the custom restrictions. This oversight allows any code executed within this environment to bypass the intended security model entirely.
From a technical perspective, the vulnerability exploits the fact that Python's standard library modules operate at a lower level than high-level application logic. By importing pathlib or io, an attacker can construct file paths and open handles using methods that are not intercepted by the restricted_open wrapper. For instance, pathlib.Path allows for robust path manipulation and direct access to files regardless of the current working directory restrictions imposed by higher-level abstractions. Similarly, io.open serves as a built-in function that provides low-level I/O operations which can circumvent custom file system hooks if those hooks do not explicitly monitor these specific module calls. This represents a classic case where security controls are applied at an insufficient layer of abstraction, leaving lower-level primitives exposed to exploitation.
The operational impact of this vulnerability is severe, as it effectively nullifies the sandboxing mechanism designed to protect against malicious plugin execution. An attacker who gains access to execute code within this environment can read sensitive configuration files, exfiltrate private keys or certificates stored on disk, and write arbitrary data back into the system. This capability transforms a contained scripting error into a full remote code execution scenario with persistent file system modifications. In contexts where openssl_encrypt is used to process untrusted input from external sources, such as web applications or automated pipelines, this vulnerability could lead to significant data breaches, integrity violations, and potential compromise of underlying infrastructure depending on the privileges under which the Python interpreter runs.
This flaw aligns closely with CWE-250, which describes execution without required privilege checks, and more specifically CWE-749, where a system fails to enforce security restrictions for users or processes. In terms of offensive cybersecurity frameworks, this vulnerability facilitates techniques associated with MITRE ATT&CK T1083, file and directory discovery, as well as T1560, archive collected data, since the attacker can systematically enumerate and extract files from the host system. The bypass mechanism also relates to CWE-20, improper input validation, because the sandbox failed to validate or block access through alternative API endpoints that achieve similar outcomes to restricted operations.
Mitigation strategies must prioritize immediate upgrading of the openssl_encrypt package to version 1.4.0 or later, where these specific module restrictions have been implemented. In environments where upgrading is not immediately feasible, administrators should consider running such processes within isolated containers with strict filesystem permissions using Linux capabilities like CAP_DAC_OVERRIDE removed. Additionally, implementing a robust security policy that restricts the import of dangerous standard library modules via sys.modules manipulation can provide an additional layer of defense. It is also advisable to audit all plugin code for any usage of pathlib or io.open and enforce static analysis rules that flag these imports in sandboxed contexts. Regular penetration testing focusing on escape techniques from restricted execution environments should be conducted to identify similar gaps in other security controls.