CVE-2017-7500 in RPM
Summary
by MITRE
It was found that rpm did not properly handle RPM installations when a destination path was a symbolic link to a directory, possibly changing ownership and permissions of an arbitrary directory, and RPM files being placed in an arbitrary destination. An attacker, with write access to a directory in which a subdirectory will be installed, could redirect that directory to an arbitrary location and gain root privilege.
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Analysis
by VulDB Data Team • 05/01/2023
The vulnerability identified as CVE-2017-7500 represents a critical privilege escalation flaw within the rpm package management system that affects numerous Linux distributions. This vulnerability stems from improper handling of symbolic link traversal during package installation processes, specifically when destination paths are symbolic links pointing to directories. The flaw allows attackers to manipulate the installation environment in ways that can result in arbitrary directory ownership changes and unauthorized placement of rpm files in unintended locations. The root cause lies in the rpm utility's failure to properly validate and resolve symbolic links before performing directory operations, creating a path traversal condition that can be exploited by malicious actors. This issue directly violates security principles by allowing unauthorized modification of system directories and potential privilege escalation to root level access.
The technical exploitation of this vulnerability occurs when an attacker possesses write permissions to a directory that will be used as a target for package installation. During the rpm installation process, if the target directory path contains a symbolic link that points to another location, the rpm utility fails to properly resolve this link and instead operates on the target directory that the symbolic link points to. This misbehavior can be leveraged to redirect package file installations to arbitrary locations on the filesystem, potentially allowing attackers to place malicious files in system directories with elevated privileges. The flaw is particularly dangerous because it can be exploited without requiring direct root access initially, as attackers can manipulate the installation environment to gain control over critical system directories. This behavior creates a scenario where standard security controls are bypassed, as the system's permission model is circumvented through the symbolic link manipulation.
The operational impact of CVE-2017-7500 extends beyond simple privilege escalation to encompass broader system compromise capabilities. When successfully exploited, this vulnerability can enable attackers to modify system binaries, install backdoors, or alter critical system configuration files, potentially leading to complete system compromise. The vulnerability affects all versions of rpm that do not properly implement symbolic link resolution during installation processes, making it widespread across affected Linux distributions. Organizations running systems with outdated rpm versions remain vulnerable, particularly those with less frequent update cycles or systems where package management is not properly monitored. The exploitation requires minimal privileges initially, making it particularly dangerous in environments where users have write access to directories that may be used during package installation, such as in shared development environments or systems with less restrictive file permissions.
Mitigation strategies for CVE-2017-7500 focus on both immediate patching and operational security improvements. The primary recommendation involves updating rpm to versions that properly handle symbolic link resolution during installation processes, which addresses the root cause of the vulnerability. System administrators should implement strict package management policies that prevent unauthorized users from having write access to directories that may be used during package installation. Additionally, monitoring and auditing of package installation activities should be enhanced to detect unusual installation patterns or unauthorized modifications to system directories. Organizations should also consider implementing file integrity monitoring solutions that can detect when critical system files are modified through package installation processes. From a security controls perspective, this vulnerability aligns with CWE-367 weakness category related to time-of-check to time-of-use conditions, and can be mapped to ATT&CK techniques involving privilege escalation through package management manipulation. The vulnerability demonstrates the importance of proper input validation and path resolution in system utilities, highlighting the need for robust security practices in package management systems that are fundamental to system integrity and security.