CVE-2025-6019 in libblockdev
Summary
by MITRE • 06/19/2025
A Local Privilege Escalation (LPE) vulnerability was found in libblockdev. Generally, the "allow_active" setting in Polkit permits a physically present user to take certain actions based on the session type. Due to the way libblockdev interacts with the udisks daemon, an "allow_active" user on a system may be able escalate to full root privileges on the target host. Normally, udisks mounts user-provided filesystem images with security flags like nosuid and nodev to prevent privilege escalation. However, a local attacker can create a specially crafted XFS image containing a SUID-root shell, then trick udisks into resizing it. This mounts their malicious filesystem with root privileges, allowing them to execute their SUID-root shell and gain complete control of the system.
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Analysis
by VulDB Data Team • 08/09/2025
The vulnerability CVE-2025-6019 represents a critical local privilege escalation flaw within the libblockdev library that leverages improper interaction between Polkit authorization mechanisms and the udisks daemon. This issue specifically targets systems where the "allow_active" Polkit setting is configured to permit physically present users to perform certain administrative actions. The vulnerability stems from a fundamental design flaw in how libblockdev communicates with udisks during filesystem operations, creating an unexpected pathway for privilege escalation that bypasses normal security controls.
The technical exploitation mechanism involves a sophisticated attack vector that combines filesystem manipulation with privilege escalation techniques. An attacker with local access can create a specially crafted XFS filesystem image containing a SUID-root shell binary, then utilize the udisks daemon's resizing functionality to mount this malicious image. The udisks daemon, which normally applies security flags such as nosuid and nodev during mounting operations, fails to properly enforce these protections when processing filesystems manipulated through the libblockdev interface. This failure allows the malicious filesystem to be mounted with root privileges, enabling execution of the SUID-root shell and complete system compromise.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally undermines the security model of modern Linux systems that rely on proper filesystem mounting semantics and user authorization controls. Attackers can leverage this flaw to gain root access without requiring additional authentication mechanisms, making it particularly dangerous in multi-user environments or systems where physical access is possible. The vulnerability affects systems where udisks is actively managing filesystem operations and where the Polkit allow_active setting is configured, potentially impacting desktop environments, servers, and containerized applications that utilize these components for storage management.
Security mitigations for CVE-2025-6019 should focus on immediate patching of affected libblockdev versions and careful review of Polkit policies to ensure that allow_active settings are not overly permissive in environments where physical security cannot be guaranteed. System administrators should implement monitoring for unusual udisks daemon activity and filesystem mounting operations that could indicate exploitation attempts. Additionally, the vulnerability aligns with CWE-276 (Improper Default Permissions) and CWE-732 (Incorrect Permission Assignment for Critical Resource) categories, while the attack methodology follows patterns consistent with ATT&CK technique T1068 (Local Privilege Escalation) and T1548.1 (Abuse Elevation Control Mechanism). Organizations should also consider implementing additional controls such as mandatory access controls, filesystem integrity monitoring, and regular security audits of storage management components to prevent exploitation of similar vulnerabilities in the broader system attack surface.