SecureLayer7’s security researchers have released technical details and proof of concept (POC) for the security vulnerability CVE-2025-6019, which affects Linux distributions relying on the udisksd daemon and libblockdev backend, including Fedora and SUSE. This vulnerability allows users in the allow_active group to gain root privileges through local privilege escalation (LPE), and it can be easily exploited in misconfigured environments.
The report states:“This vulnerability allows users in the allow_active group to escalate their privileges to root under specific conditions.”
The root cause of the CVE-2025-6019 vulnerability lies in the way udisksd (a system daemon for managing disks) communicates via D-Bus. It incorrectly assumes that group membership is sufficient to perform privileged disk operations (such as mounting, formatting, and unlocking).
SecureLayer7 explains:“The issue arises from improper handling of user permissions during inter-process communication (IPC) via D-Bus.” In other words, any user in the allow_active group can trick the system into performing root-level operations without actual root credentials.
The affected systems include:
- Fedora 40+
- SUSE Linux with udisks2 and libblockdev
- Systems using the allow_active group to obtain disk-related permissions
Attackers can exploit this vulnerability if the following conditions are met:
- udisksd is installed and running.
- The user belongs to the allow_active group.
- The system’s Polkit/D-Bus validation rules are weak or set to default.
SecureLayer7 points out:“The layered breakdown of permissions, combined with erroneous assumptions of group-based trust, creates a dangerous security vulnerability, especially on shared or multi-user systems.”
SecureLayer7 reproduced the vulnerability in a Fedora 40 container that included udisks2, libblockdev, and a test user. Using a simple Python script or D-Bus command line call, the vulnerability triggered a mount operation:
print("[*] Attempting to mount via udisksctl...") result = subprocess.run(["udisksctl", "mount", "-b", "/dev/loop0"], stdout=subprocess.PIPE, stderr=subprocess.PIPE, universal_newlines=True) print("STDOUT:", result.stdout) print("STDERR:", result.stderr) If the group and service are misconfigured: udisksctl mount -b /dev/loop0Result:
Mounted /dev/loop0 at /run/media/testuser/loop0 The researchers confirmed:“This confirms that non-root users can perform mount operations controlled by root.” In some cases, combining this with volume management APIs could lead to a complete root privilege leak.
Developers have patched the logic to ensure that only root users can mount disks – even if they belong to allow_active.
The report states:“The patch introduces a stricter validation path, eliminating the group-only trust model and fully transitioning to a policy implementation based on polkitd + uid.”
Additionally, Fedora has strengthened the Polkit rules for /org/freedesktop/UDisks2/Manager, closing the loophole in D-Bus policy execution.
If you are a system administrator or Linux desktop user:
- Immediately update udisks2 and libblockdev to the latest patched versions.
- Audit and minimize the use of the allow_active group.
- Review and strengthen Polkit policies for disk and volume operations.
- Avoid exposing udisksd on multi-user systems without a sandbox.
Reference link:
https://blog.securelayer7.net/cve-2025-6019-local-privilege-escalation/