CVE-2017-7541 in Linux
Summary
by MITRE
The brcmf_cfg80211_mgmt_tx function in drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c in the Linux kernel before 4.12.3 allows local users to cause a denial of service (buffer overflow and system crash) or possibly gain privileges via a crafted NL80211_CMD_FRAME Netlink packet.
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Analysis
by VulDB Data Team • 12/13/2022
The vulnerability identified as CVE-2017-7541 represents a critical buffer overflow flaw within the Linux kernel's wireless subsystem, specifically affecting the brcmf_cfg80211_mgmt_tx function in the Broadcom brcm80211 driver implementation. This vulnerability exists in kernel versions prior to 4.12.3 and exposes systems to both denial of service conditions and potential privilege escalation attacks. The flaw manifests when processing NL80211_CMD_FRAME Netlink packets, which are used for wireless management frame transmission in the Linux wireless subsystem. The affected driver component handles management frames for Broadcom wireless network adapters, making this vulnerability particularly concerning for systems utilizing Broadcom wireless hardware.
The technical nature of this vulnerability stems from inadequate input validation and buffer boundary checking within the wireless management frame processing code. When a malicious local user sends a crafted NL80211_CMD_FRAME packet, the kernel function fails to properly validate the size or content of the management frame data before attempting to copy it into a fixed-size buffer. This classic buffer overflow condition occurs because the code does not perform sufficient bounds checking on the user-supplied data length parameter, allowing an attacker to write beyond the allocated buffer boundaries. The vulnerability is classified as a CWE-121, which represents stack-based buffer overflow conditions, and more specifically aligns with CWE-787, representing out-of-bounds write conditions. The flaw represents a direct violation of the principle of least privilege and input validation, as the kernel should never trust user-provided data without proper sanitization.
The operational impact of this vulnerability extends beyond simple system crashes, potentially enabling privilege escalation attacks that could allow local users to elevate their privileges within the system. In a typical denial of service scenario, the buffer overflow causes a kernel memory corruption that results in a system crash or reboot, effectively denying legitimate users access to the wireless network functionality. However, the more serious implications arise when considering that this vulnerability could be exploited to execute arbitrary code with kernel-level privileges, particularly when combined with other exploitation techniques or when the system is running with elevated permissions. The attack vector requires local access to the system, meaning that an attacker must already have user-level access to exploit this vulnerability, but the potential for privilege escalation makes it particularly dangerous in multi-user environments or when combined with other local privilege escalation vulnerabilities.
Mitigation strategies for CVE-2017-7541 primarily focus on applying the official kernel security patches released with kernel version 4.12.3 and subsequent releases. System administrators should immediately update their Linux kernel installations to versions 4.12.3 or later to address this vulnerability. Additionally, network administrators should consider implementing network segmentation and access controls to limit local user access to systems running vulnerable kernel versions. The vulnerability's classification under the ATT&CK framework would place it within the Privilege Escalation category, specifically under techniques involving kernel exploits or local privilege escalation through memory corruption vulnerabilities. Organizations should also implement monitoring solutions to detect unusual patterns of Netlink packet traffic that might indicate exploitation attempts. For systems where kernel updates are not immediately possible, implementing additional security controls such as mandatory access controls, user namespace restrictions, and limiting local user accounts' ability to interact with wireless management interfaces can provide additional defense in depth. The vulnerability underscores the importance of regular kernel maintenance and security patching in maintaining system integrity and preventing exploitation of known vulnerabilities in widely deployed kernel subsystems.