CVE-2025-27727 in Windows
Summary
by MITRE • 04/08/2025
Improper link resolution before file access ('link following') in Windows Installer allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 05/31/2026
This vulnerability represents a critical privilege escalation flaw in the windows installer component that stems from improper handling of symbolic links during file access operations. The issue occurs when the installer processes symbolic links without adequately validating or resolving them before accessing underlying files, creating a pathway for malicious actors to manipulate the installation process and gain elevated system privileges. The vulnerability specifically affects the local privilege escalation vector where an authorized user with standard permissions can exploit this weakness to execute code with administrative privileges. According to the common weakness enumeration framework CWE-59, this represents a classic link following vulnerability where the system fails to properly resolve symbolic links before performing file operations, potentially allowing attackers to redirect file access to arbitrary locations on the filesystem. The attack typically involves creating malicious symbolic links that point to protected system files or directories, which the installer then accesses without proper validation, effectively bypassing normal access controls and security boundaries. This flaw operates within the windows installer service context where file operations are performed with elevated privileges, making the impact particularly severe. The vulnerability manifests when the installer encounters symbolic links during the installation process and follows them without proper verification of the target file's integrity or access permissions. From an operational perspective, this weakness allows attackers to escalate their privileges from standard user level to administrator level, potentially enabling full system compromise and persistent access. The attack requires local system access and can be executed through carefully crafted installation packages or by manipulating existing installation processes. The impact extends beyond simple privilege escalation as it can be leveraged to install malicious software, modify system files, or establish backdoors within the target environment. Security professionals should note that this vulnerability aligns with several attack techniques documented in the attack tree framework, particularly those involving privilege escalation and lateral movement within compromised systems. The vulnerability's exploitation is considered relatively straightforward for attackers who understand the windows installer architecture and can manipulate symbolic link creation within the installation context. Organizations should implement immediate mitigations including restricting symbolic link creation permissions, applying relevant microsoft security updates, and monitoring for suspicious installation activities. The vulnerability highlights the importance of proper input validation and secure file handling practices in system components that operate with elevated privileges, emphasizing the need for comprehensive security controls throughout the software development lifecycle. Microsoft has addressed this issue through security patches that enhance the installer's symbolic link resolution process and implement additional validation checks. The remediation process should include comprehensive system updates, along with security configuration reviews to prevent unauthorized symbolic link creation in critical installation directories.