CVE-2018-1196 in Spring Boot
Summary
by MITRE
Spring Boot supports an embedded launch script that can be used to easily run the application as a systemd or init.d linux service. The script included with Spring Boot 1.5.9 and earlier and 2.0.0.M1 through 2.0.0.M7 is susceptible to a symlink attack which allows the "run_user" to overwrite and take ownership of any file on the same system. In order to instigate the attack, the application must be installed as a service and the "run_user" requires shell access to the server. Spring Boot application that are not installed as a service, or are not using the embedded launch script are not susceptible.
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Analysis
by VulDB Data Team • 03/31/2022
The vulnerability identified as CVE-2018-1196 resides within Spring Boot's embedded launch script functionality that facilitates deployment of applications as system services on linux platforms. This flaw specifically affects versions 1.5.9 and earlier, as well as 2.0.0.M1 through 2.0.0.M7, creating a critical security weakness in the service initialization process. The vulnerability operates through a symlink attack vector that fundamentally compromises the integrity of the system's file permissions and ownership model. When a Spring Boot application is configured as a service using the embedded launch script, the script executes with elevated privileges and establishes a specific run_user context that governs file system access patterns. The technical flaw manifests when the launch script fails to properly validate symbolic link references during service initialization, allowing a malicious user with shell access to manipulate the symlink chain and subsequently overwrite arbitrary files on the system.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass complete system compromise through unauthorized file modification. An attacker exploiting this weakness can leverage the run_user context to overwrite critical system files, configuration data, or application binaries with malicious content. This attack vector represents a classic privilege escalation vulnerability that aligns with CWE-59 and CWE-275 categories, specifically addressing issues related to improper handling of symbolic links and inadequate permission validation. The attack requires the target application to be installed as a service, and the attacker must possess shell access to the server, making it a targeted vulnerability that cannot be exploited remotely. However, the combination of these prerequisites creates a significant risk when considering that many production environments have compromised shell access points or where users with legitimate access might be exploited through social engineering or other means.
From an attack framework perspective, this vulnerability maps directly to the privilege escalation techniques documented in the MITRE ATT&CK framework under the Privilege Escalation category, specifically targeting the technique of "Path Interception" and "Exploitation for Privilege Escalation." The vulnerability demonstrates how embedded system components can introduce security flaws that bypass normal access controls and privilege boundaries. Organizations using Spring Boot applications in production environments face particular risk since the vulnerability affects the service initialization process where applications typically run with elevated privileges. The attack chain begins with obtaining shell access, followed by manipulation of the symbolic link structure to redirect file operations, ultimately allowing the attacker to overwrite any file accessible to the run_user account. This creates a potential for complete system compromise through modification of critical system files, configuration databases, or even application binaries that could lead to persistent backdoors or data exfiltration capabilities.
The recommended mitigation strategies focus on immediate version upgrades to Spring Boot 2.0.0.M8 or later versions where this vulnerability has been addressed through proper validation of symbolic link references in the launch script. Organizations should also implement comprehensive service deployment reviews to ensure that applications are not unnecessarily configured with elevated privileges, and that proper file system permissions are enforced through additional security controls such as file integrity monitoring and privilege separation. System administrators should conduct thorough audits of all Spring Boot applications installed as services to identify potential exposure and implement mandatory access controls that prevent the execution of potentially malicious symbolic link manipulations. The vulnerability serves as a reminder of the critical importance of validating all file system operations in privileged contexts and demonstrates how seemingly benign system integration features can introduce significant security risks when proper validation controls are absent.