Sudo's Chroot Misstep: Unpacking CVE-2025-32463 Privilege Escalation

Introduction

In the ever-evolving landscape of Linux security, even trusted utilities like sudo can introduce critical vulnerabilities. CVE-2025-32463, a recently disclosed privilege escalation flaw, underscores this reality by enabling local attackers to escalate privileges to root through sudo's chroot option. Given sudo's ubiquity across Linux systems, understanding and mitigating this vulnerability is crucial for security professionals.

Technical Information

CVE-2025-32463 stems from a design flaw introduced in sudo version 1.9.14, where path resolution occurs within a user-controlled chroot environment prematurely during sudoers policy evaluation. Specifically, when sudo is invoked with the -R or --chroot option, it attempts to load /etc/nsswitch.conf from the attacker-defined chroot directory. Attackers exploit this behavior by placing a malicious nsswitch.conf file that references attacker-controlled shared libraries. This results in arbitrary code execution with root privileges, bypassing standard sudoers restrictions.

The vulnerability specifically affects sudo versions 1.9.14 through 1.9.17. Systems without chroot configurations or those running versions prior to 1.9.14 or patched versions after 1.9.17p1 are not vulnerable.

Proof of Concept

The double-free vulnerability in Sudo's per-command chroot feature, identified as CVE-2023-27320, arises when a specific configuration in the sudoers file includes a CHROOT setting. This setting allows a user to execute commands within a specified chroot environment. The flaw is triggered during the processing of such a sudoers rule, leading to the user_cmnd variable being freed twice. This double-free condition can result in undefined behavior, including potential system crashes or, in certain scenarios, arbitrary code execution. It's important to note that this vulnerability is only exploitable if the sudoers configuration contains a per-command CHROOT directive matching the current host. Therefore, systems without such configurations are not affected. To mitigate this issue, administrators should remove any sudoers rules containing the CHROOT setting or update Sudo to version 1.9.13p2, where the vulnerability has been addressed. (openwall.com)

Patch Information

To address CVE-2025-32463, the sudo project released version 1.9.17p1, implementing two critical changes:

1. Reversion of Path Resolution Behavior: The flawed path resolution logic introduced in sudo 1.9.14 has been reverted, preventing exploitation via malicious shared libraries.

2. Deprecation of the Chroot Feature: The chroot functionality has been deprecated due to security complexities and limited usage, with removal planned for future releases.

Administrators should upgrade to sudo 1.9.17p1 immediately to mitigate this vulnerability effectively.

Affected Systems and Versions

• Vulnerable: sudo versions 1.9.14 through 1.9.17
• Not Vulnerable: sudo versions prior to 1.9.14 and patched versions 1.9.17p1 and later
• Specific configurations vulnerable: Systems using the -R or --chroot option with NSS configuration files

Vendor Security History

The sudo project has historically demonstrated prompt responses to security vulnerabilities, typically releasing patches within days of disclosure. However, recurring vulnerabilities in legacy features like chroot indicate ongoing challenges in maintaining secure implementations of complex functionalities.

References

• NVD CVE-2025-32463
• Official CVE Entry
• Sudo Security Advisories
• Ubuntu Security Notice USN-7604-1
• Openwall PoC
• Stratascale Analysis
• OSS Security Mailing List

Security teams should prioritize addressing this vulnerability due to its potential impact and ease of exploitation.

Source: This report was created using AI