CVE-2013-1772 in Linux
Summary
by MITRE
The log_prefix function in kernel/printk.c in the Linux kernel 3.x before 3.4.33 does not properly remove a prefix string from a syslog header, which allows local users to cause a denial of service (buffer overflow and system crash) by leveraging /dev/kmsg write access and triggering a call_console_drivers function call.
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Analysis
by VulDB Data Team • 05/05/2021
The vulnerability identified as CVE-2013-1772 represents a critical buffer overflow flaw in the Linux kernel's logging subsystem that specifically affects kernel versions 3.x prior to 3.4.33. This issue resides within the log_prefix function located in kernel/printk.c, which is responsible for managing syslog header formatting and prefix handling. The flaw occurs when the kernel processes log messages and fails to properly sanitize or remove prefix strings from syslog headers during console driver operations. The vulnerability is particularly concerning because it can be exploited by local attackers who possess write access to the /dev/kmsg device, which is a privileged interface that allows direct kernel message injection.
The technical exploitation of this vulnerability involves leveraging the /dev/kmsg write capability to inject malformed log messages that trigger the vulnerable log_prefix function. When the system processes these specially crafted messages, the function fails to properly handle buffer boundaries during prefix string removal operations, leading to memory corruption that manifests as a buffer overflow condition. This overflow directly impacts the call_console_drivers function, which is responsible for routing kernel log messages to appropriate console drivers. The improper handling of prefix strings creates a scenario where the kernel's memory management becomes compromised, ultimately resulting in system instability and potential complete system crashes. This behavior aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of improper input validation in kernel space operations.
The operational impact of this vulnerability extends beyond simple denial of service to potentially compromising system availability and stability in production environments. Local attackers with access to /dev/kmsg can exploit this flaw to crash the entire system, effectively creating a persistent denial of service condition that requires system reboot to resolve. The vulnerability's exploitation requires minimal privileges since /dev/kmsg access is typically available to local users, making it particularly dangerous in multi-user environments or systems where privilege escalation is possible. Systems running affected kernel versions are at risk of arbitrary crashes, which can lead to data loss, service interruptions, and potential compromise of system integrity. This vulnerability particularly affects server environments and embedded systems where kernel stability is paramount, and where local access might be more readily available than in highly restricted environments.
Mitigation strategies for CVE-2013-1772 focus primarily on kernel version updates to 3.4.33 or later, which contain the necessary patches to address the buffer overflow in the log_prefix function. System administrators should prioritize applying these kernel updates across all affected systems, particularly in production environments where the vulnerability could be exploited to cause service disruptions. Additional protective measures include restricting access to /dev/kmsg through proper file system permissions and access controls, implementing monitoring for unusual console driver activity, and maintaining comprehensive system logging to detect potential exploitation attempts. Organizations should also consider implementing runtime protections such as kernel hardening patches, address space layout randomization, and other security enhancements that can help mitigate the impact of similar vulnerabilities. The ATT&CK framework categorizes this vulnerability under privilege escalation and denial of service techniques, as it allows local users to gain elevated system impact through kernel-level memory corruption, making it a significant concern for system security posture and compliance requirements.