CVE-2015-8946 in eCryptfs
Summary
by MITRE
ecryptfs-setup-swap in eCryptfs before 111 does not prevent the unencrypted swap partition from activating during boot when using GPT partitioning and certain versions of systemd, which allows local users to obtain sensitive information via unspecified vectors.
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Analysis
by VulDB Data Team • 09/09/2022
The vulnerability identified as CVE-2015-8946 affects the eCryptfs filesystem encryption utility, specifically the ecryptfs-setup-swap component within eCryptfs versions prior to 111. This flaw represents a critical security oversight in the handling of encrypted swap partitions during system boot processes, particularly when systems utilize GPT partitioning schemes alongside specific versions of systemd. The vulnerability stems from inadequate handling of swap partition activation sequences, creating a potential information disclosure risk that could be exploited by local attackers.
The technical flaw manifests when eCryptfs attempts to configure swap partitions for encrypted systems using GPT partitioning. During the boot process, the ecryptfs-setup-swap utility fails to properly prevent unencrypted swap partitions from activating before the encryption layer is fully initialized. This creates a window of opportunity where sensitive data might be written to unencrypted swap space, potentially exposing encrypted content or system credentials to unauthorized local users. The issue is specifically exacerbated when systemd versions interact with GPT partitioning schemes, as the timing and sequence of system initialization processes become misaligned with encryption layer activation.
The operational impact of this vulnerability extends beyond simple information disclosure, as it fundamentally undermines the security assumptions of encrypted systems. Local users who gain access to the system can exploit this weakness to recover sensitive information from swap space, potentially including cached passwords, encryption keys, or other confidential data that should remain protected. The vulnerability affects systems where eCryptfs is used for full disk encryption, particularly those employing GPT partition tables and specific systemd versions, making it relevant to a significant portion of modern Linux distributions that utilize these technologies. This weakness essentially creates a backdoor for information leakage that bypasses the intended encryption protections.
Security mitigations for CVE-2015-8946 primarily involve updating to eCryptfs version 111 or later, which includes proper handling of swap partition activation sequences and prevents unencrypted swap from activating during boot. System administrators should also consider implementing additional security controls such as disabling swap entirely for highly sensitive systems or ensuring that swap partitions are properly encrypted using tools like dm-crypt. The vulnerability aligns with CWE-200, which addresses "Information Exposure," and represents a specific instance where the lack of proper input validation and system initialization sequence management creates security weaknesses. From an ATT&CK framework perspective, this vulnerability maps to T1005, "Data from Local System," and T1059, "Command and Scripting Interpreter," as it allows for information gathering through system-level access and potentially command execution within the compromised environment. Organizations should also implement proper monitoring for unauthorized swap usage and consider using alternative encryption solutions that properly handle boot-time initialization sequences to prevent similar vulnerabilities from affecting their security posture.