CVE-2017-18226 in jabberd2
Summary
by MITRE
The Gentoo net-im/jabberd2 package through 2.6.1 sets the ownership of /var/run/jabber to the jabber account, which might allow local users to kill arbitrary processes by leveraging access to this account for PID file modification before a root script executes a "kill -TERM `cat /var/run/jabber/filename.pid`" command.
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Analysis
by VulDB Data Team • 01/12/2020
The vulnerability identified as CVE-2017-18226 resides within the Gentoo net-im/jabberd2 package version 2.6.1 and earlier, presenting a significant local privilege escalation risk through improper file ownership and process management. This flaw specifically affects the handling of PID files within the jabber service execution environment, creating a window of opportunity for malicious local users to exploit the system's process termination mechanism. The vulnerability stems from the package's configuration where the /var/run/jabber directory is owned by the jabber user account, allowing unauthorized modification of PID files that are subsequently used by root-level scripts during service operations.
The technical exploitation of this vulnerability occurs through a race condition scenario where a local attacker with access to the jabber account can modify or replace PID files in the /var/run/jabber directory before a root script executes its termination command. When the root script performs the operation "kill -TERM `cat /var/run/jabber/filename.pid`", it reads the PID from the file and attempts to terminate the corresponding process. However, if an attacker has modified the PID file to contain a different process ID, the root script will terminate an unintended process, potentially allowing the attacker to kill arbitrary processes running with elevated privileges. This represents a classic case of improper privilege management and file system access control where a lower-privileged user can manipulate system-level operations through carefully crafted file modifications.
The operational impact of this vulnerability extends beyond simple process termination, as it fundamentally undermines the security model of the system by allowing local users to potentially disrupt critical services or escalate their privileges through strategic process manipulation. Attackers could use this vulnerability to kill essential system processes, disrupt service availability, or even target processes running with higher privileges to gain further access. This vulnerability aligns with CWE-276, which addresses improper file permissions and access control, and represents a form of privilege escalation that could be leveraged as part of a broader attack chain. The attack pattern follows the principles outlined in the ATT&CK framework under privilege escalation techniques, specifically targeting process manipulation and file system compromise to achieve unauthorized system control.
Mitigation strategies for CVE-2017-18226 must focus on proper file ownership and access control mechanisms to prevent local users from modifying critical PID files. System administrators should ensure that the /var/run/jabber directory and its contents are owned by the root user with appropriate permissions that prevent modification by the jabber account. The recommended approach involves implementing strict file system permissions where only the root user can write to the PID directory and its files, while the jabber account should only have read access. Additionally, the root script should implement proper validation checks to verify the authenticity and integrity of PID files before executing termination commands, and should consider using more secure methods such as process name verification or direct process identification rather than relying solely on PID file contents. Organizations should also implement regular security audits to identify similar privilege escalation vulnerabilities in other system components and ensure that all service management scripts properly validate their inputs and maintain appropriate access controls.