Linux Privilege Escalation (CVE-2025-6019): Root Access Via udisksd & libblockdev, PoC Available

Security researchers from SecureLayer7 published the technical details and a proof-of-concept exploit for a security vulnerability, CVE-2025-6019, affecting Linux distributions that rely on the udisksd daemon and libblockdev backend, including Fedora and SUSE. The flaw allows local privilege escalation (LPE) to root for users in the allow_active group, and it’s disturbingly easy to exploit in misconfigured environments.

“This vulnerability allows a user in the allow_active group to escalate privileges to root under specific conditions,” the report states.

The root of CVE-2025-6019 lies in how udisksd, a system daemon for managing disks, communicates over D-Bus. It incorrectly trusts group membership as sufficient authority for privileged disk operations, such as mounting, formatting, and unlocking.

“The issue stems from improper handling of the user’s authority during inter-process communications (IPC) via D-Bus,” SecureLayer7 explains.

In other words, any user in the allow_active group could fool the system into executing root-level actions—without needing actual root credentials.

The affected systems include

• Fedora 40+
• SUSE Linux with udisks2 and libblockdev
• Systems using allow_active group for disk-related permissions

Attackers can leverage the vulnerability if:

• udisksd is installed and running.
• A user is in the allow_active group.
• The system has weak or default Polkit/D-Bus validation rules.

“The layered breakdown in permissions, combined with a flawed assumption of group-based trust, creates a dangerous security gap, especially on shared or multi-user systems,” SecureLayer7 notes.

SecureLayer7 replicated the exploit on a Fedora 40 container with udisks2, libblockdev, and a test user. Using a simple Python-based script or a D-Bus command-line call, the exploit 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/loop0

Result:

Mounted /dev/loop0 at /run/media/testuser/loop0 

“This confirmed root-controlled mounting from a non-root user,” the researchers confirmed. In some cases, chaining this with volume management APIs could enable full root compromise.

Developers patched the logic to ensure only root users can mount disks—even if they belong to allow_active.

“The patch introduced a stricter verification path that eliminates the group-only trust model and shifts entirely to polkitd + uid-based policy enforcement,” the report states.

Additionally, Fedora hardened the Polkit rules for /org/freedesktop/UDisks2/Manager, closing loopholes in D-Bus policy enforcement.

If you’re a sysadmin or Linux desktop user:

• Immediately update udisks2 and libblockdev to the latest patched versions.
• Audit and minimize use of allow_active group.
• Review and tighten Polkit policies for disk and volume operations.
• Avoid exposing udisksd on multi-user systems without sandboxing.

Related Posts:

• Critical Linux Root Exploit Chain Discovered in PAM & UDisks, Affecting Major Distros
• Authentication Bypass in Deepin D-Bus Proxy Service (CVE-2025-23222): A Critical Design Flaw Exposed
• Fedora 27 Live ISO Image Release: Fixed CPU Vulnerability
• Fedora starts to support Google Chrome and Steam

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Written by

@DdoS · Security Researcher

Do Son

Do Son is the Founder and Editor of SecurityOnline.info. Working in cybersecurity since 2013, he reports on vulnerabilities, malware, and emerging threats, providing timely analysis to help organizations and individuals stay ahead of evolving risks.