PoC Released for Linux Privilege Escalation Vulnerability via udisksd and libblockdev

A proof-of-concept exploit for a critical local privilege escalation vulnerability affecting major Linux distributions, including Fedora and SUSE environments.

The vulnerability, designated CVE-2025-6019, allows unprivileged users to gain root access through exploitation of the udisksd daemon and its backend library libblockdev, creating significant security risks for multi-user systems and shared environments.

The vulnerability exploits a fundamental vulnerability in how the udisksd daemon processes D-Bus communication requests from users in the allow_active group.

When properly configured systems receive disk-related operations through D-Bus calls, the daemon incorrectly assumes that group membership alone provides sufficient authorization for sensitive operations.

This trust boundary violation enables attackers to bypass intended security controls and execute privileged operations with root permissions.

The attack vector centers on improper handling of user authority during inter-process communications via D-Bus. Security researchers discovered that the udisksd daemon fails to validate the invoking user’s context adequately, instead relying solely on group-based privilege checks.

This design flaw creates an exploitable pathway where D-Bus calls can be manipulated to trigger unauthorized privileged operations, reads the analysis from SecureLayer7.

Linux Privilege Escalation Vulnerability

Static analysis of the udisks2 and libblockdev source code revealed several concerning patterns in the privilege escalation pathway. The vulnerable execution flow follows the pattern: udisks_daemon_handle_mount → polkit_check → blkdev_mount.

This sequence allows unprivileged users to cause udisksd to execute mount operations with root permissions, effectively bypassing the intended security model.

The exploitation process requires minimal technical sophistication, making it particularly dangerous. Attackers need only membership in the allow_active group and the ability to execute udisksctl commands.

The proof-of-concept demonstrates that a simple command like udisksctl mount -b /dev/loop0 can result in root-controlled mounting operations from non-root users, potentially leading to full system compromise.

The vulnerability affects a broad range of Linux distributions that implement udisks2 and libblockdev as part of their desktop environments. Fedora and SUSE systems are particularly vulnerable due to their default configurations, which often include users in the allow_active group for desktop functionality.

The security issue is especially concerning for shared computing environments, multi-user systems, and any deployment where privilege separation is critical.

Distribution maintainers have responded with security updates that address the core vulnerability through multiple mechanisms. The primary fix involves stricter UID-based verification rather than relying solely on group membership. Updated code now requires both group membership and appropriate UID context before allowing privileged operations.

Additionally, Polkit rules have been strengthened to enforce more granular permission checks. The updated implementation includes enhanced validation paths that eliminate the group-only trust model and implement comprehensive policy enforcement through polkitd integration.

System administrators should immediately update udisks2 and libblockdev packages to patched versions. Organizations should also audit their group-based permissions and implement stricter polkit rules to prevent similar vulnerabilities.

This incident underscores the importance of thorough threat modeling for system services that interact with IPC buses and handle hardware operations, particularly when assumptions about user privilege boundaries may be flawed.

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