CVE-2016-4685 in iOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 10.1 is affected. The issue involves the "iTunes Backup" component, which improperly hashes passwords, making it easier to decrypt files.
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Analysis
by VulDB Data Team • 08/15/2020
The vulnerability identified as CVE-2016-4685 represents a critical cryptographic weakness in Apple's iTunes backup functionality affecting iOS versions prior to 10.1. This flaw resides within the password hashing mechanism used to protect backup files, creating a significant security risk for users who rely on iTunes for device synchronization and data backup operations. The issue demonstrates Apple's failure to implement robust password-based key derivation functions, leaving user data potentially accessible through brute force or dictionary attack methods that would otherwise be computationally infeasible.
The technical implementation flaw stems from the use of weak hashing algorithms or improper key derivation processes within the iTunes backup component. When users set passwords for their iOS backups, the system should employ strong cryptographic functions such as PBKDF2 with sufficient iteration counts or modern alternatives like Argon2 to protect against password cracking attempts. However, the vulnerable implementation appears to use insufficiently complex hashing mechanisms that allow attackers to reverse engineer backup passwords more efficiently than expected, potentially compromising sensitive data stored in encrypted backups including contacts, messages, photos, and application data.
From an operational impact perspective, this vulnerability creates a substantial risk for iOS users who maintain encrypted backups of their devices. Attackers with access to backup files can leverage the weak password hashing to recover user credentials and decrypt backup contents, effectively bypassing Apple's intended security measures. The vulnerability affects not just individual users but also organizations that may have deployed iOS devices in enterprise environments where backup encryption is expected to provide data protection. This weakness undermines the security model of iOS backup functionality and creates potential exposure for personal information, corporate data, and sensitive communications stored in encrypted backup archives.
The security implications extend beyond simple data recovery, as this vulnerability aligns with attack patterns described in the MITRE ATT&CK framework under credential access and defense evasion techniques. The weakness creates opportunities for adversaries to perform offline password cracking attacks against backup files, potentially enabling further compromise of user accounts and systems. Organizations should consider this vulnerability when assessing their mobile device security posture, particularly in environments where iOS devices are used to store sensitive corporate information. The issue also highlights the importance of proper key derivation functions as outlined in CWE-326, which addresses the weakness of insufficient encryption strength, and CWE-256, which covers improper password hashing implementations.
Mitigation strategies should focus on immediate remediation through iOS version updates to 10.1 or later, which address the underlying cryptographic implementation issues. Users should also consider implementing additional security controls such as regular backup rotation, limiting the amount of sensitive data stored in encrypted backups, and employing alternative backup solutions with stronger encryption mechanisms. Security administrators should monitor for potential exploitation attempts and ensure that backup files are stored securely with appropriate access controls. The vulnerability underscores the critical importance of proper cryptographic implementation in mobile security systems and serves as a reminder of the need for thorough security testing of all encryption components within mobile operating systems and backup solutions.