CVE-2026-74899

openssl_encrypt Python sandbox escape enables arbitrary command execution.

• CVSS 9.3
• 95
• Input Validation and Sanitization
• Remote

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.

CVE

CVE-2026-74899

CWE

95

CVSS base score

9.3

Published

2026-08-17

OWASP

A03 Injection

Orthogonal defect classification

Checking

Code defect classification

Incorrect Check

Category

Input Validation and Sanitization

Subcategory

Command Injection

Accessibility scope

Remote

Impact

Arbitrary Code Execution

Fixed by upgrading

Yes

Solution

Upgrade jupyter-server-proxy to version 1.4.0 or later.

class IsolatedPluginExecutor:
    def execute(self, plugin_code: str):
        """
        Executes plugin code in a restricted environment.
        """
        # For convenience, some built-in types are exposed to the plugin.
        restricted_builtins = {
            'len': len,
            'str': str,
            'dict': dict,
        }

        environment = {
            '__builtins__': restricted_builtins,
        }

        # VULNERABLE: Exposing type objects like 'dict' in exec builtins allows class hierarchy traversal.
        exec(plugin_code, environment)

class IsolatedPluginExecutor:
    def execute(self, plugin_code: str):
        """
        Executes plugin code in a restricted environment.
        """
        # Only safe functions are exposed; types are not.
        restricted_builtins = {
            'len': len,
            'str': str,
        }

        environment = {
            '__builtins__': restricted_builtins,
        }

        # FIX: Do not expose any type objects, preventing introspection-based sandbox escapes.
        exec(plugin_code, environment)

__VAITP_MODEL_REFUSED__

@misc{vaitp:cve202674899,
  title        = {{openssl_encrypt Python sandbox escape enables arbitrary command execution.}},
  author       = {Bogaerts, Fr\'ed\'eric and Ivaki, Naghmeh and Fonseca, Jos\'e},
  year         = {2026},
  note         = {VAITP Python Vulnerability Dataset, entry CVE-2026-74899},
  howpublished = {\url{https://netpack.pt/vaitp/vulnerability/CVE-2026-74899/}}
}