CVE-2011-2517 in Linux
Summary
by MITRE
Multiple buffer overflows in net/wireless/nl80211.c in the Linux kernel before 2.6.39.2 allow local users to gain privileges by leveraging the CAP_NET_ADMIN capability during scan operations with a long SSID value.
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Analysis
by VulDB Data Team • 12/02/2021
The vulnerability identified as CVE-2011-2517 represents a critical buffer overflow condition within the Linux kernel's wireless subsystem, specifically in the nl80211.c file responsible for handling wireless network operations. This flaw affects kernel versions prior to 2.6.39.2 and demonstrates a classic security weakness where insufficient input validation leads to memory corruption. The vulnerability operates through the wireless scanning functionality, which is commonly used by network management tools and wireless drivers to discover available networks in the vicinity. When a user with the CAP_NET_ADMIN capability attempts to perform a wireless scan operation with an excessively long SSID value, the kernel fails to properly validate the input length before copying it into a fixed-size buffer, creating a condition where adjacent memory can be overwritten.
The technical exploitation of this vulnerability requires an attacker to possess the CAP_NET_ADMIN capability, which is a Linux capability that grants network administration privileges including the ability to configure wireless devices and perform network scans. This capability is typically available to users in the root group or applications running with elevated privileges. The buffer overflow occurs during the processing of wireless scan results where the kernel attempts to store SSID information in a predetermined buffer size that cannot accommodate oversized input. The flaw stems from inadequate bounds checking in the wireless subsystem's input handling code, allowing maliciously crafted SSID values to exceed the allocated buffer space and overwrite adjacent memory locations. This memory corruption can potentially be leveraged to execute arbitrary code within kernel space, providing attackers with elevated privileges and complete system compromise.
The operational impact of CVE-2011-2517 extends beyond simple privilege escalation as it represents a fundamental security weakness in the kernel's wireless subsystem that could be exploited by local attackers with minimal privileges. The vulnerability's exploitation requires only the ability to run processes with CAP_NET_ADMIN capability, which is commonly available to system administrators and certain network management applications. This makes the vulnerability particularly dangerous as it can be triggered through legitimate wireless management operations, making detection more challenging. The attack surface includes any system running affected kernel versions that performs wireless scanning operations, particularly servers and workstations with wireless network interfaces. The potential for privilege escalation to root level access makes this vulnerability particularly attractive to attackers seeking persistent access to systems, as demonstrated by the weakness mapping to CWE-121 which covers stack-based buffer overflow conditions. The vulnerability also aligns with ATT&CK technique T1068 which covers local privilege escalation through kernel exploits, making it a significant concern for enterprise security.
Mitigation strategies for CVE-2011-2517 focus primarily on kernel version updates and capability restriction practices. The most effective solution involves upgrading to Linux kernel version 2.6.39.2 or later, where the buffer overflow has been patched through proper input validation and bounds checking implementations. System administrators should also implement strict capability management policies to minimize the exposure of CAP_NET_ADMIN to unnecessary processes and users. The vulnerability highlights the importance of proper input validation in kernel space operations and demonstrates why security patches for kernel components must be applied promptly. Additionally, monitoring wireless scanning activities and implementing network access controls can help detect potential exploitation attempts. Organizations should also consider implementing kernel hardening techniques such as stack canaries and address space layout randomization to make exploitation more difficult even if the vulnerability remains unpatched. The flaw serves as a reminder of the critical importance of maintaining up-to-date kernel versions and proper privilege separation in enterprise security practices.