Overview
This article discusses CVE-2025-66479, a vulnerability discovered in Anthropic Sandbox Runtime, a lightweight tool designed to enforce filesystem and network restrictions on processes. This vulnerability allows sandboxed code to potentially bypass network restrictions, enabling unauthorized network requests outside the intended sandbox environment.
Technical Details
CVE-2025-66479 arises from a flaw in the network sandboxing logic of Anthropic Sandbox Runtime versions prior to 0.0.16. Specifically, if the sandbox policy *did not* explicitly configure any allowed domains, the sandbox runtime would fail to properly enforce the network sandbox. This meant that any network requests made by the sandboxed code would not be blocked, effectively negating the intended network isolation.
The root cause is a conditional check that did not handle the case where no domains were explicitly allowed, leading to a bypass of the intended blocking mechanism.
CVSS Analysis
Currently, a CVSS score has not been assigned for CVE-2025-66479. However, given the potential for arbitrary code execution and data exfiltration due to the network sandbox bypass, it is advisable to treat this vulnerability with a high level of concern. The severity is currently listed as N/A, but a more formal CVSS score may be released in the future.
Possible Impact
The impact of CVE-2025-66479 can be significant, especially if the sandbox is intended to protect sensitive data or critical systems. A successful exploit could lead to:
- Data Exfiltration: Sandboxed code could potentially transmit sensitive data to external servers.
- Remote Code Execution: If the sandboxed code is able to connect to and exploit other systems on the network.
- Compromise of Host System: In some scenarios, vulnerabilities in network services reachable from the sandbox could be exploited to gain access to the host system.
Mitigation or Patch Steps
The recommended mitigation is to upgrade Anthropic Sandbox Runtime to version 0.0.16 or later. This version includes a patch that addresses the flawed network sandboxing logic.
To upgrade, follow the instructions provided in the Anthropic Sandbox Runtime documentation. For those unable to immediately upgrade, consider implementing compensating controls such as network segmentation and monitoring to detect and prevent unauthorized network activity from sandboxed environments. Note that these compensating controls do not fully address the underlying vulnerability, but provide a defense-in-depth approach.
