CVE-2012-3409 in ecryptfs-utils
Summary
by MITRE
ecryptfs-utils: suid helper does not restrict mounting filesystems with nosuid,nodev which creates a possible privilege escalation
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Analysis
by VulDB Data Team • 12/20/2019
The vulnerability identified as CVE-2012-3409 affects the ecryptfs-utils package, which provides encryption utilities for the ecryptfs filesystem. This issue resides in the suid helper program responsible for managing filesystem mounting operations. The flaw stems from inadequate restriction mechanisms within the helper program that fails to properly validate mount options when creating encrypted filesystem mounts. When users execute the suid helper with specific mount parameters, the system does not adequately enforce security policies that would normally prevent mounting filesystems with dangerous combinations of mount options such as nosuid and nodev. This oversight creates a potential privilege escalation pathway where unprivileged users could leverage the helper program to mount filesystems with elevated privileges. The vulnerability is particularly concerning because it directly exploits the setuid mechanism that is designed to grant temporary elevated privileges for specific operations while maintaining system security boundaries. According to CWE-276, this represents a classic improper privilege management vulnerability where the system fails to properly control access to privileged operations. The flaw aligns with ATT&CK technique T1068 which involves exploiting legitimate credentials and privileges to gain access to restricted resources. The security implications extend beyond simple privilege escalation as the vulnerability allows for potential bypass of kernel security modules that normally enforce mount option restrictions.
The technical implementation of this vulnerability occurs within the ecryptfs helper program that is typically invoked through the mount.ecryptfs command. When the helper receives mount requests, it processes the mount options without sufficiently validating whether the combination of options would create a security risk. Specifically, the helper does not properly restrict mounting filesystems with the nosuid and nodev options, which when combined with other mount parameters can create a scenario where the mounted filesystem inherits elevated privileges or bypasses normal security checks. This occurs because the helper program does not validate that the mount options provided would maintain the security context that the ecryptfs system expects. The flaw is particularly dangerous because the suid helper is designed to operate with elevated privileges to perform filesystem operations, but the validation logic fails to ensure that these elevated privileges are not used to create mount points with dangerous security configurations. The vulnerability demonstrates poor input validation and privilege management practices that are commonly associated with CWE-78 and CWE-269 categories. The mount options nosuid and nodev are specifically designed to prevent execution of setuid binaries and device access respectively, but the helper program fails to enforce these restrictions properly.
The operational impact of this vulnerability extends beyond simple privilege escalation to potentially enable more sophisticated attacks within the target system. An attacker could exploit this vulnerability to mount encrypted filesystems with configurations that bypass normal security restrictions, potentially allowing for access to sensitive data or system resources that should remain protected. The vulnerability affects systems using ecryptfs for transparent encryption of user home directories or other sensitive filesystem areas, making it particularly dangerous for enterprise environments where data protection is paramount. Attackers could leverage this flaw to create mount points that allow execution of arbitrary code with elevated privileges or to bypass normal access controls that would otherwise prevent unauthorized access to encrypted data. The impact is especially severe because the vulnerability can be exploited by unprivileged users who would normally not have access to such powerful mounting capabilities. This flaw represents a critical weakness in the kernel's security model as it allows bypassing the normal mount option validation that should occur when mounting filesystems with elevated privileges. The vulnerability also has implications for defense-in-depth strategies since it can be combined with other techniques to create more complex attack vectors. Systems that rely on ecryptfs for data protection may be rendered less secure than expected due to this flaw, potentially exposing encrypted data to unauthorized access or modification.
Mitigation strategies for CVE-2012-3409 should focus on immediate patching of the ecryptfs-utils package to address the flawed validation logic in the suid helper program. System administrators should ensure that all affected systems are updated to versions that properly validate mount options and enforce security restrictions on filesystem mounting operations. The patch should specifically address the validation of mount parameters to ensure that combinations of options like nosuid and nodev are properly restricted when mounting encrypted filesystems. Organizations should also consider implementing additional monitoring of mount operations and suid binary execution to detect potential exploitation attempts. Network segmentation and access controls should be reviewed to limit the potential impact if exploitation occurs, particularly in environments where multiple users share systems. The vulnerability highlights the importance of proper privilege management and input validation, making it essential to review similar helper programs and setuid binaries for analogous issues. Security configurations should be audited to ensure that mount options are properly enforced and that the principle of least privilege is maintained. System hardening measures should include disabling unnecessary mount options and ensuring that filesystem mounting operations are properly logged and monitored for suspicious activity. The remediation process should also involve reviewing and updating security policies to address the specific threat model presented by this vulnerability, ensuring that encrypted filesystems maintain their intended security properties even when accessed through potentially compromised helper programs.