CVE-2015-5898 in Watch
Summary
by MITRE
CFNetwork in Apple iOS before 9 relies on the hardware UID for its cache encryption key, which makes it easier for physically proximate attackers to obtain sensitive information by obtaining this UID.
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Analysis
by VulDB Data Team • 06/19/2022
The vulnerability described in CVE-2015-5898 represents a critical weakness in Apple's CFNetwork implementation within iOS versions prior to 9.0, where the system's cache encryption mechanism relies on a hardware-specific identifier known as the UID for generating encryption keys. This design flaw fundamentally undermines the security of cached network data by creating a predictable cryptographic foundation that adversaries can exploit. The UID serves as a static hardware identifier that remains consistent across device usage, making it a deterministic factor in the encryption process rather than a dynamic element that would provide proper cryptographic security.
The technical exploitation of this vulnerability occurs through physical proximity attacks where an attacker can obtain the device's UID through various means such as device recovery processes, forensic analysis, or direct hardware access. Once obtained, this UID allows attackers to reconstruct the encryption keys used for CFNetwork cache encryption, thereby enabling them to decrypt and access sensitive information stored in the network cache. This weakness directly relates to CWE-326, which addresses the use of weak encryption or the absence of encryption in security-critical applications, and specifically demonstrates how static identifiers can compromise cryptographic implementations. The vulnerability essentially transforms what should be a secure encrypted cache into an easily exploitable data repository.
The operational impact of this vulnerability extends beyond simple information disclosure, as it allows attackers to access cached network data that may include session tokens, authentication credentials, browsing history, and other sensitive network communications. This creates a significant risk for users who rely on iOS devices for business or personal activities requiring secure network communications, as the cached data becomes accessible to anyone who can obtain the device's UID. The threat model particularly affects users in environments where physical security cannot be guaranteed, such as shared workspaces, public transportation, or locations where devices might be temporarily unattended. This vulnerability also aligns with ATT&CK technique T1552.001, which covers the exploitation of cached credentials, and demonstrates how hardware-level identifiers can be leveraged to bypass application-level security controls.
Mitigation strategies for this vulnerability require immediate system updates to iOS 9.0 or later versions where Apple addressed the issue by implementing more robust encryption key generation mechanisms that do not rely on static hardware identifiers. Organizations should also implement additional security measures such as enabling device encryption, implementing strong screen lock policies, and establishing procedures for secure device handling and disposal. Network administrators should consider deploying additional monitoring solutions to detect unusual access patterns that might indicate exploitation attempts. The fix implemented by Apple demonstrates proper security engineering practices by moving away from deterministic key derivation based on hardware identifiers toward more secure methods that incorporate dynamic elements and proper cryptographic key management practices, aligning with industry standards for secure software development and the principles outlined in the NIST Cybersecurity Framework.