CVE-2016-5847 in SAPCAR
Summary
by MITRE
SAP SAPCAR allows local users to change the permissions of arbitrary files and consequently gain privileges via a hard link attack on files extracted from an archive, possibly related to SAP Security Note 2327384.
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Analysis
by VulDB Data Team • 10/25/2024
SAPCAR is a utility distributed by SAP that serves as a command-line tool for extracting and creating archive files within the SAP environment. This tool operates with elevated privileges during archive extraction processes, creating a potential attack surface that adversaries can exploit to escalate privileges locally on systems running SAP applications. The vulnerability stems from improper handling of file extraction operations where SAPCAR does not adequately validate or sanitize symbolic links and hard links present within archive files. When an archive containing maliciously crafted hard links is extracted, the utility follows these links and modifies permissions on arbitrary system files, potentially allowing attackers to gain unauthorized access to sensitive resources. This vulnerability specifically impacts systems where SAPCAR is used to process untrusted archive files, which commonly occurs in enterprise environments where software distribution and system maintenance operations involve unpacking various archive formats.
The technical flaw resides in the insufficient validation of file attributes during the extraction process, particularly concerning hard links and symbolic links. When SAPCAR processes an archive containing a hard link, it follows the link and modifies the permissions of the target file rather than properly handling the link itself. This behavior creates a privilege escalation vector because the utility typically runs with administrative or root privileges during extraction operations, allowing an attacker to manipulate file permissions on critical system resources. The vulnerability is closely related to the broader class of hard link attacks that fall under CWE-59, which describes improper handling of hard links in file systems. These attacks exploit the fundamental property that multiple directory entries can point to the same file data, enabling attackers to redirect file operations to arbitrary locations on the system. The specific implementation issue manifests when the extraction utility does not properly check for the existence of hard links or symbolic links before attempting to modify file permissions, leading to unintended access control modifications.
The operational impact of CVE-2016-5847 extends beyond simple privilege escalation to encompass potential system compromise and data integrity violations. Attackers exploiting this vulnerability can gain unauthorized access to system files, modify critical configuration settings, or establish persistent access mechanisms within the SAP environment. The attack requires local system access and the ability to place malicious archives on the target system, but once executed, it can provide attackers with elevated privileges that persist across system reboots. This vulnerability particularly affects enterprise environments where SAP applications are extensively deployed, as these systems often process numerous archive files from various sources including software updates, patches, and third-party components. The risk is compounded by the fact that many organizations have automated processes that automatically extract archives, making the exploitation more likely to succeed without direct user interaction. Organizations using SAPCAR for routine system maintenance operations are especially vulnerable, as these processes often occur with elevated privileges and may process archives from untrusted sources.
Mitigation strategies for CVE-2016-5847 focus on both immediate defensive measures and long-term architectural improvements. Organizations should immediately apply the security patch provided by SAP in SAP Security Note 2327384, which addresses the hard link handling issue within SAPCAR. System administrators should also implement strict file permission controls and monitor archive extraction operations for suspicious activities, particularly those involving hard links or symbolic links. The principle of least privilege should be enforced by ensuring that SAPCAR and similar utilities operate with minimal required privileges during archive processing. Additionally, organizations should establish secure software distribution practices that validate and sanitize all archive files before processing, implementing content filtering mechanisms that detect and reject potentially malicious hard links. From an operational security perspective, regular vulnerability assessments should include scanning for systems running vulnerable versions of SAPCAR, and security monitoring solutions should be configured to alert on unusual file permission changes during extraction operations. The mitigation approach aligns with ATT&CK technique T1068 which covers privilege escalation through local exploitation, and the broader category of file system manipulation techniques that attackers use to gain unauthorized access to system resources.