CVE-2018-16864 in Enterprise Session Border Controller
Summary
by MITRE
An allocation of memory without limits, that could result in the stack clashing with another memory region, was discovered in systemd-journald when a program with long command line arguments calls syslog. A local attacker may use this flaw to crash systemd-journald or escalate his privileges. Versions through v240 are vulnerable.
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Analysis
by VulDB Data Team • 08/31/2023
The vulnerability identified as CVE-2018-16864 represents a critical memory management flaw in systemd-journald, the logging service component of the systemd suite that is widely deployed across Linux distributions. This issue manifests as an unbounded memory allocation pattern that occurs when programs with excessively long command line arguments invoke the syslog function, creating a scenario where memory consumption grows without proper constraints. The vulnerability resides in the journal daemon's handling of command line arguments, specifically when processing long argv strings that are passed to the logging system. The flaw enables a local attacker to manipulate memory allocation behavior in a way that can cause system instability and potential privilege escalation. The vulnerability is particularly concerning because systemd-journald typically runs with elevated privileges as part of the system's core logging infrastructure, making it a prime target for exploitation.
The technical implementation of this vulnerability stems from the journal daemon's insufficient validation of command line argument lengths when processing incoming log messages. When a program with an exceptionally long command line invokes syslog, the systemd-journald service allocates memory to store these arguments without imposing reasonable limits on the allocation size. This unbounded memory allocation can lead to stack memory corruption and memory region collision, where the allocated memory inadvertently overwrites adjacent memory areas including other critical system structures. The flaw demonstrates characteristics consistent with CWE-770, which addresses allocation of resources without limits or with inadequate limits, and can be categorized under CWE-122, which deals with insufficient synchronization. The vulnerability's exploitation path involves a local attacker crafting a program with an extremely long argv string to trigger the memory allocation behavior, potentially leading to stack smashing or memory corruption that can result in denial of service or privilege escalation.
The operational impact of CVE-2018-16864 extends beyond simple system instability to encompass potential privilege escalation capabilities that make it particularly dangerous in production environments. When exploited, the vulnerability can cause systemd-journald to crash, leading to logging service disruption that may affect system monitoring and security auditing capabilities. More critically, the memory corruption resulting from unbounded allocation can be leveraged by local attackers to execute arbitrary code with elevated privileges, potentially allowing them to gain root access to the affected system. This vulnerability affects all versions of systemd through v240, which represents a significant portion of Linux systems deployed in enterprise and cloud environments. The exploitability of this flaw is enhanced by the fact that systemd-journald typically operates with high privileges and is continuously running, making it an attractive target for persistent attackers. The vulnerability's impact is further amplified by the fact that many applications and system services regularly invoke syslog functions, increasing the attack surface.
Mitigation strategies for CVE-2018-16864 should prioritize immediate patching of affected systemd versions to v241 or later, where the memory allocation limits have been properly implemented. System administrators should also consider implementing additional monitoring and alerting around systemd-journald processes to detect unusual memory consumption patterns that might indicate exploitation attempts. The implementation of system call restrictions through capabilities or seccomp-bpf filters can help limit the potential impact of such vulnerabilities by restricting what operations systemd-journald can perform. Organizations should also review their logging configurations to ensure that command line arguments are properly sanitized before being passed to logging functions. From an operational security perspective, the vulnerability aligns with ATT&CK technique T1059.003, which covers execution through command and scripting interpreter, and T1068, which addresses local privilege escalation through system services. Regular vulnerability assessments should include checks for systemd versions and ensure that proper memory management practices are in place to prevent similar issues in other system components. The vulnerability serves as a reminder of the critical importance of proper input validation and resource management in system services that operate with elevated privileges.