Redazione RHC : 8 July 2025 09:16
A proof-of-concept (PoC) exploit for a critical vulnerability that allows local privilege escalation has been developed, affecting several major Linux distributions, such as Fedora and SUSE. The vulnerability, tracked as CVE-2025-6019, allows unprivileged users to gain root access by exploiting the udisksd daemon and its libblockdev backend library, posing a significant security risk to multi-user systems and shared environments.
The vulnerability exploits a fundamental vulnerability in the way the udisksd daemon processes D-Bus communication requests from users of the allow_active group. When properly configured systems receive disk operations via D-Bus calls, the daemon incorrectly assumes that group membership alone provides sufficient permission for sensitive operations.
Recall that the udisksd daemon is a system component on Linux responsible for managing storage devices (hard drives, SSDs, USB sticks, CDs/DVDs, etc.). This PoC allows attackers to bypass expected security controls and perform privileged operations with root permissions.
The attack vector focuses on improper management of user authority during interprocess communications via D-Bus. Security researchers have discovered that the udisksd daemon fails to properly validate the context of the invoking user, instead relying solely on group-based privilege checks.
According to SecureLayer7’s analysis, this design flaw creates an exploitable path where D-Bus calls can be manipulated to trigger unauthorized privileged operations. Static analysis of the udisks2 and libblockdev source code revealed several troubling patterns in the privilege escalation path. The vulnerable execution flow follows the following pattern: udisks_daemon_handle_mount → polkit_check → blkdev_mount.
This sequence allows unprivileged users to cause udisksd to perform root mount operations, effectively circumventing the intended security model. The exploit process requires minimal technical sophistication, which makes it particularly dangerous. Attackers only need membership in the allow_active group and the ability to execute udisksctl commands.
The proof of concept demonstrates that a simple command such as udisksctl mount -b /dev/loop0 can cause root-controlled mount operations by non-root users, potentially leading to the compromise of the entire system. The vulnerability affects a wide range of Linux distributions that implement udisks2 and libblockdev in 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 of particular concern for shared computing environments, multi-user systems, and any distribution where privilege separation is critical. Distribution managers responded with security updates that address the core vulnerability through several mechanisms. The core fix includes stricter UID-based checking, rather than relying solely on group membership. The updated code now requires both group membership and an appropriate UID context before allowing privileged operations.
System administrators should immediately update the udisks2 and libblockdev packages to the correct versions. Organizations should also verify group-based permissions and implement stricter polkit rules to prevent similar vulnerabilities.
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