CVE-2013-7264 in Linux
Summary
by MITRE
The l2tp_ip_recvmsg function in net/l2tp/l2tp_ip.c in the Linux kernel before 3.12.4 updates a certain length value before ensuring that an associated data structure has been initialized, which allows local users to obtain sensitive information from kernel stack memory via a (1) recvfrom, (2) recvmmsg, or (3) recvmsg system call.
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Analysis
by VulDB Data Team • 06/04/2021
The vulnerability identified as CVE-2013-7264 represents a critical information disclosure flaw within the Linux kernel's Layer 2 Tunneling Protocol implementation. This issue exists in the l2tp_ip_recvmsg function located in net/l2tp/l2tp_ip.c, affecting kernel versions prior to 3.12.4. The flaw manifests when the kernel processes incoming L2TP packets through standard socket operations, creating a scenario where sensitive kernel memory can be exposed to local attackers. The vulnerability stems from improper order of operations during packet processing, specifically where a length value is updated before verifying that the associated data structure has been properly initialized.
The technical exploitation of this vulnerability occurs through three primary system calls: recvfrom, recvmmsg, and recvmsg, all of which are standard socket operations used by applications to receive data. When these system calls are invoked against L2TP sockets, the kernel's l2tp_ip_recvmsg function processes the incoming packet data without first ensuring that the necessary data structures are properly initialized. This sequence error allows an attacker to manipulate the packet processing flow such that uninitialized kernel memory contents are inadvertently copied to user space, effectively leaking kernel stack information. The vulnerability is classified as a classic information disclosure issue, with the potential to expose sensitive data including cryptographic keys, passwords, or other confidential information stored in kernel memory.
From an operational perspective, this vulnerability presents a significant risk to systems running affected kernel versions, particularly those utilizing L2TP networking protocols for VPN connections or tunneling services. Local attackers who can execute processes on the target system can leverage this flaw to gain access to kernel memory contents, potentially compromising the security of the entire system. The impact extends beyond simple information disclosure as the leaked data could contain credentials, session keys, or other sensitive information that could be used for privilege escalation or further attacks. According to CWE classification, this vulnerability maps to CWE-248: Uncaught Exception, as the improper handling of uninitialized data structures leads to unexpected behavior. The ATT&CK framework categorizes this as a privilege escalation technique under T1068: Exploitation for Privilege Escalation, since successful exploitation could provide attackers with elevated system privileges.
Mitigation strategies for CVE-2013-7264 primarily focus on kernel version updates, with the most effective solution being the upgrade to Linux kernel version 3.12.4 or later where the vulnerability has been patched. System administrators should prioritize patching affected systems, particularly those running L2TP services or VPN configurations. Additionally, organizations can implement network segmentation to limit local access to systems, though this does not eliminate the vulnerability itself. Monitoring for suspicious socket operations and unusual network traffic patterns may help detect potential exploitation attempts, though this represents a reactive approach rather than a preventive measure. The patch addresses the root cause by ensuring proper initialization order of data structures before length values are updated, preventing the leakage of uninitialized kernel memory contents. Organizations should also consider implementing kernel hardening measures and maintaining up-to-date security patches for all system components to prevent similar vulnerabilities from being exploited.