CVE-2009-1338 in Linux
Summary
by MITRE
The kill_something_info function in kernel/signal.c in the Linux kernel before 2.6.28 does not consider PID namespaces when processing signals directed to PID -1, which allows local users to bypass the intended namespace isolation, and send arbitrary signals to all processes in all namespaces, via a kill command.
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Analysis
by VulDB Data Team • 04/18/2025
The vulnerability described in CVE-2009-1338 represents a critical flaw in the Linux kernel's signal handling mechanism that fundamentally undermines process isolation principles. This issue exists within the kill_something_info function located in kernel/signal.c, where the kernel fails to properly account for PID namespaces when processing signals directed to PID -1. The problem manifests specifically in Linux kernel versions prior to 2.6.28, creating a pathway for local attackers to circumvent the intended security boundaries that PID namespaces are designed to enforce. The flaw enables malicious users to send arbitrary signals to all processes across all namespaces, effectively breaking the isolation that these namespaces were implemented to provide.
The technical implementation of this vulnerability stems from the kernel's improper handling of the special PID -1 value, which is typically used to send signals to all processes in the current process group. When PID -1 is used in the context of signal delivery, the kernel should respect namespace boundaries and only target processes within the current namespace. However, the flawed implementation fails to check whether the current process is operating within a PID namespace and consequently ignores the namespace context when processing these signals. This oversight allows a local attacker executing within one namespace to send signals that propagate across all namespaces, creating a severe escalation of privileges and potential system-wide disruption.
From an operational impact perspective, this vulnerability represents a significant threat to containerized environments and systems utilizing PID namespaces for process isolation. The ability to send arbitrary signals to processes across all namespaces means that an attacker can potentially terminate critical system processes, disrupt services, or trigger denial of service conditions that span multiple isolated environments. This vulnerability directly violates the principle of least privilege and namespace isolation that modern container technologies rely upon for security. The impact extends beyond simple signal manipulation to potentially enable more sophisticated attacks where an attacker can use this capability to escalate privileges, gain unauthorized access to resources, or cause system instability that affects the entire host system.
The vulnerability aligns with CWE-284, which addresses improper access control in software systems, and demonstrates how inadequate consideration of namespace boundaries can lead to privilege escalation. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and defense evasion, as it allows local users to bypass security controls that should normally prevent cross-namespace operations. The attack vector requires local system access but provides significant capabilities for system disruption and potential compromise. Organizations using Linux systems with PID namespace support should prioritize patching this vulnerability, as it represents a fundamental flaw in the kernel's security model that affects the integrity of process isolation mechanisms. The fix implemented in kernel version 2.6.28 properly accounts for PID namespace boundaries when processing signals to PID -1, ensuring that signal delivery respects namespace isolation and maintains the security guarantees that these namespaces are designed to provide.