CVE-2019-8339 in Sysdig
Summary
by MITRE
An issue was discovered in Sysdig through 0.24.2, as used in Falco through 0.14.0 and other products. A bypass allows local users to run malicious code without being detected because record_event_consumer in driver/main.c in sysdig-probe.ko (and falco-probe.ko) mishandles a free space calculation.
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Analysis
by VulDB Data Team • 09/23/2023
The vulnerability identified as CVE-2019-8339 represents a critical security flaw within the Sysdig monitoring and logging platform ecosystem, specifically affecting versions through 0.24.2 in the sysdig-probe kernel module and falco-probe kernel module. This issue creates a significant bypass mechanism that undermines the integrity of system monitoring capabilities by allowing local attackers to execute malicious code while evading detection mechanisms. The flaw resides in the driver component of the sysdig-probe.ko kernel module, which is responsible for capturing system events and maintaining the security posture of the monitored environment. The vulnerability specifically manifests in the record_event_consumer function within the driver/main.c file, where improper handling of free space calculations creates an exploitable condition that can be leveraged by malicious actors.
The technical implementation of this vulnerability stems from a buffer management flaw that occurs during event recording operations within the kernel space of the sysdig probe module. When the system processes and records system events, the record_event_consumer function performs calculations to determine available buffer space for storing event data. However, due to incorrect free space calculation logic, an attacker can manipulate the buffer management system to create conditions where malicious code execution can occur without triggering the normal detection mechanisms. This bypass mechanism operates at the kernel level, making it particularly dangerous as it can circumvent traditional security controls that rely on system call monitoring and event logging. The flaw essentially creates a scenario where the system believes it has sufficient buffer space to handle legitimate events while simultaneously allowing malicious code to execute in the same context without proper monitoring or alerting.
The operational impact of CVE-2019-8339 extends far beyond simple privilege escalation, as it fundamentally compromises the integrity of the entire monitoring and detection infrastructure. Local users who exploit this vulnerability can execute arbitrary code with kernel-level privileges, potentially leading to complete system compromise and persistent access. The implications are particularly severe in environments where Sysdig and Falco are deployed for security monitoring, as the vulnerability allows attackers to remain undetected while performing malicious activities such as privilege escalation, data exfiltration, or establishing backdoors. This bypass directly violates the fundamental security assumptions of the monitoring system, as the very tools designed to detect and alert on suspicious activities become ineffective against this specific attack vector. The vulnerability undermines the trust model of security monitoring platforms, where administrators rely on these systems to provide comprehensive visibility into system activities and potential threats.
The remediation approach for this vulnerability requires immediate patching of affected systems, with version 0.24.3 and later releases containing the necessary fixes for the buffer management calculations in the sysdig-probe kernel module. Organizations should implement comprehensive monitoring of their Sysdig and Falco deployments to identify any potential exploitation attempts before patches are applied. The fix addresses the core buffer management logic in the record_event_consumer function, ensuring proper calculation of free space and preventing the conditions that enable the bypass. Security teams should also conduct thorough vulnerability assessments to identify systems running affected versions and prioritize patching based on risk exposure. Additionally, implementing network segmentation and privilege separation can provide additional defense-in-depth measures while awaiting patch deployment. This vulnerability aligns with CWE-129, which addresses improper validation of buffer boundaries, and maps to ATT&CK technique T1059.007 for command and scripting interpreter, as attackers can leverage this bypass to execute malicious code undetected within the system monitoring environment.