CVE-2017-7836 in Firefox
Summary
by MITRE
The "pingsender" executable used by the Firefox Health Report dynamically loads a system copy of libcurl, which an attacker could replace. This allows for privilege escalation as the replaced libcurl code will run with Firefox's privileges. Note: This attack requires an attacker have local system access and only affects OS X and Linux. Windows systems are not affected. This vulnerability affects Firefox < 57.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 03/22/2023
The CVE-2017-7836 vulnerability represents a critical privilege escalation flaw within Firefox's health reporting mechanism on macOS and Linux systems. This vulnerability specifically targets the pingsender executable component that Firefox employs to collect and transmit health data to Mozilla's servers. The security issue arises from the dynamic loading behavior of the pingsender utility which relies on loading a system-installed copy of the libcurl library rather than using a bundled or statically linked version. This design decision creates a significant attack surface that malicious actors can exploit to elevate their privileges within the system.
The technical flaw stems from the insecure dynamic library loading practice where the pingsender executable searches for libcurl in standard system library paths without proper validation or integrity checking mechanisms. When an attacker gains local system access, they can replace the legitimate libcurl library with a malicious version that executes arbitrary code with the elevated privileges of the Firefox process. This occurs because the replaced library code runs with the same privileges as the pingsender executable, which typically operates with sufficient permissions to access system resources. The vulnerability is classified under CWE-427 Uncontrolled Search Path Element, which specifically addresses the dangerous practice of allowing programs to load libraries from insecure locations. This weakness directly enables attackers to perform library injection attacks that bypass normal privilege boundaries.
The operational impact of this vulnerability is particularly severe for users running affected Firefox versions on macOS and Linux systems. Since the attack requires only local system access, attackers who have already compromised a user's account or gained physical access to the machine can leverage this flaw to escalate their privileges to the level of the Firefox process. This privilege escalation capability can potentially allow attackers to access sensitive user data, modify system configurations, or establish persistent access to the compromised system. The vulnerability affects all Firefox versions prior to 57, making it a significant concern for users who have not updated their browsers. The attack vector is particularly concerning because it operates silently in the background and can be exploited without user interaction, making detection and prevention challenging for system administrators.
Mitigation strategies for CVE-2017-7836 primarily focus on updating to Firefox version 57 or later, which addressed the insecure library loading behavior by implementing proper library validation and using bundled dependencies instead of system libraries. Organizations should also consider implementing privilege separation measures where Firefox processes run with minimal required privileges and by monitoring for unauthorized modifications to system library paths. Additionally, system administrators can employ file integrity monitoring solutions to detect changes to critical system libraries and implement strict access controls on system directories where libraries are stored. The vulnerability highlights the importance of secure coding practices and adherence to the principle of least privilege in software development. This issue aligns with ATT&CK technique T1068 Privilege Escalation through the use of insecure library loading to gain elevated system access, demonstrating how seemingly minor implementation flaws can create significant security risks in widely deployed software applications.