CVE-2018-16865 in systemd-journald
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 many entries are sent to the journal socket. A local attacker, or a remote one if systemd-journal-remote is used, may use this flaw to crash systemd-journald or execute code with journald privileges. Versions through v240 are vulnerable.
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Analysis
by VulDB Data Team • 06/26/2023
The vulnerability identified as CVE-2018-16865 represents a critical memory allocation flaw in systemd-journald, the logging service component of the systemd suite. This issue manifests when the journal socket receives an excessive number of entries, creating a scenario where memory allocation occurs without proper bounds checking. The flaw stems from inadequate input validation and memory management practices within the journal daemon's processing logic, specifically when handling high-volume logging data streams. The vulnerability is particularly concerning as it affects versions through v240, indicating a long-standing issue that could have been exploited across multiple system deployments.
The technical nature of this vulnerability aligns with CWE-772, which describes "Missing Release of Resource after Effective Lifetime," and more specifically relates to improper memory management practices. When systemd-journald processes numerous entries simultaneously, it fails to implement adequate limits on memory allocation, potentially leading to stack memory corruption. The stack clashing behavior occurs because the system does not properly manage memory boundaries, allowing allocated memory to overwrite adjacent memory regions. This memory corruption can result in unpredictable behavior including process crashes or more severe exploitation opportunities. The flaw demonstrates characteristics of a memory safety issue that can be leveraged for privilege escalation attacks.
From an operational perspective, this vulnerability presents significant risk to system integrity and availability. A local attacker can exploit this flaw to crash the systemd-journald service, causing logging disruptions and potentially system instability. However, the more serious concern arises from the potential for remote exploitation when systemd-journal-remote is enabled, which allows remote systems to send log entries to the target machine. This remote attack vector expands the threat surface considerably, as attackers could potentially execute arbitrary code with the elevated privileges of the journald process. The impact extends beyond simple service disruption to encompass potential system compromise, especially in environments where journald runs with elevated permissions.
Mitigation strategies for CVE-2018-16865 should focus on immediate version updates to systemd v241 or later, where the memory allocation limits have been properly implemented. System administrators should also consider implementing monitoring for unusual logging activity patterns that might indicate exploitation attempts. Network segmentation and access controls around systems running systemd-journal-remote should be strengthened to limit exposure. Additionally, implementing proper input validation and rate limiting for journal socket connections can provide defense-in-depth measures. The ATT&CK framework categorizes this vulnerability under T1059 for command and scripting interpreter and T1068 for exploit for privilege escalation, highlighting the multi-faceted attack surface this flaw presents. Organizations should also review their logging infrastructure configurations to ensure that remote logging capabilities are properly secured and that unnecessary exposure is minimized.