CVE-2017-7558 in Linux
Summary
by MITRE
A kernel data leak due to an out-of-bound read was found in the Linux kernel in inet_diag_msg_sctp{,l}addr_fill() and sctp_get_sctp_info() functions present since version 4.7-rc1 through version 4.13. A data leak happens when these functions fill in sockaddr data structures used to export socket's diagnostic information. As a result, up to 100 bytes of the slab data could be leaked to a userspace.
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Analysis
by VulDB Data Team • 12/16/2022
The vulnerability identified as CVE-2017-7558 represents a critical kernel data leak affecting the Linux kernel version 4.7-rc1 through 4.13. This flaw manifests in the inet_diag_msg_sctp{,l}addr_fill() and sctp_get_sctp_info() functions, which are responsible for exporting socket diagnostic information through the inet_diag interface. The issue stems from improper bounds checking during the filling of sockaddr data structures, creating a scenario where kernel memory contents are inadvertently exposed to userspace processes. This type of vulnerability falls under the category of information disclosure flaws that can potentially expose sensitive kernel data to unauthorized parties.
The technical implementation of this vulnerability involves out-of-bounds read operations within the SCTP (Stream Control Transmission Protocol) socket diagnostic functions. When these functions process socket information for export, they fail to properly validate the boundaries of memory regions being accessed and copied into userspace structures. The specific flaw occurs during the population of sockaddr structures, where up to 100 bytes of adjacent kernel slab memory may be leaked. This memory leakage can contain various kernel data including sensitive information such as cryptographic keys, session tokens, or other confidential data stored in the kernel's memory space. The vulnerability is particularly concerning because it operates at the kernel level and can be exploited by unprivileged users who have access to the inet_diag interface.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially expose kernel memory contents that may contain sensitive operational data or system state information. Attackers could leverage this vulnerability to gather intelligence about the target system, potentially enabling more sophisticated attacks such as privilege escalation or targeted exploitation of other system components. The leak of up to 100 bytes of kernel slab data represents a significant risk, as this memory may contain pointers, system configuration data, or other information that could aid in further exploitation attempts. From an attacker's perspective, this vulnerability aligns with techniques described in the ATT&CK framework under the information gathering and reconnaissance phases, specifically targeting kernel-level information disclosure.
Mitigation strategies for CVE-2017-7558 require immediate patching of affected kernel versions to address the out-of-bounds read conditions in the SCTP diagnostic functions. System administrators should prioritize upgrading to kernel versions that contain the fix, typically those released after the vulnerability disclosure. Additionally, implementing proper access controls on the inet_diag interface can help limit exposure by restricting which users or processes can query socket information. Network segmentation and monitoring of socket diagnostic queries can provide early detection of potential exploitation attempts. The vulnerability's classification as a CWE-125 out-of-bounds read aligns with common security practices for preventing memory safety issues in kernel code, emphasizing the importance of bounds checking and proper input validation in kernel-space operations. Organizations should also consider implementing kernel memory protection mechanisms and regular security audits to identify similar vulnerabilities in other kernel subsystems.