CVE-2015-7799 in Linux
Summary
by MITRE
The slhc_init function in drivers/net/slip/slhc.c in the Linux kernel through 4.2.3 does not ensure that certain slot numbers are valid, which allows local users to cause a denial of service (NULL pointer dereference and system crash) via a crafted PPPIOCSMAXCID ioctl call.
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Analysis
by VulDB Data Team • 06/22/2022
The vulnerability identified as CVE-2015-7799 resides within the Linux kernel's slip driver implementation, specifically in the slhc_init function located in drivers/net/slip/slhc.c. This flaw represents a classic case of input validation failure that can be exploited by local attackers to disrupt system operations. The vulnerability affects Linux kernel versions through 4.2.3, making it a significant concern for systems running these older kernel versions. The issue stems from insufficient validation of slot numbers during the initialization process, creating a pathway for malicious manipulation of kernel memory structures.
The technical exploitation of this vulnerability occurs through a crafted PPPIOCSMAXCID ioctl command that manipulates the slot number parameters passed to the slhc_init function. When the kernel processes this ioctl call, it fails to validate that the specified slot numbers fall within acceptable ranges, allowing attackers to provide invalid slot values that result in NULL pointer dereferences. This particular flaw manifests as a NULL pointer dereference condition that leads to kernel panic and system crash, effectively causing a denial of service condition that can be exploited to disrupt normal system operations. The vulnerability operates at the kernel level, making it particularly dangerous as it can compromise the entire system stability.
From an operational impact perspective, this vulnerability creates a significant risk for systems running affected kernel versions, particularly those that may be exposed to untrusted local users or processes. The denial of service condition can result in complete system crashes, requiring manual intervention and system restarts that can disrupt critical services and operations. The vulnerability is classified under CWE-125 as an Out-of-bounds Read condition, though it manifests as a NULL pointer dereference rather than a traditional buffer overflow. The ATT&CK framework would categorize this as a privilege escalation technique through kernel exploitation, as local users can leverage this flaw to gain unauthorized system control.
Mitigation strategies for CVE-2015-7799 primarily focus on kernel version upgrades to patched releases that contain proper slot number validation. System administrators should prioritize updating to kernel versions that have addressed this specific flaw, as the vulnerability cannot be effectively mitigated through configuration changes alone. Additionally, implementing proper access controls to limit local user privileges and monitoring for unusual ioctl calls can help reduce the attack surface. The vulnerability demonstrates the importance of robust input validation in kernel space code, as even seemingly minor validation gaps can lead to critical system compromise. Organizations should also consider implementing kernel hardening measures and regularly reviewing kernel security patches to prevent similar vulnerabilities from being exploited in their environments.