CVE-2017-6437 in libplist
Summary
by MITRE
The base64encode function in base64.c in libimobiledevice libplist 1.12 allows local users to cause a denial of service (out-of-bounds read) via a crafted plist file.
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Analysis
by VulDB Data Team • 09/09/2020
The vulnerability identified as CVE-2017-6437 resides within the libimobiledevice libplist library version 1.12, specifically within the base64encode function located in base64.c. This library serves as a critical component for handling property list files on iOS devices and other mobile platforms, facilitating communication between desktop applications and mobile devices through protocols like iTunes and mobile device management systems. The flaw manifests when the base64encode function processes malformed plist files that contain crafted data structures, leading to improper memory handling during base64 encoding operations. This represents a classic out-of-bounds read vulnerability that can be exploited by local attackers who possess the ability to manipulate plist files used by the affected library.
The technical implementation of this vulnerability stems from inadequate input validation and bounds checking within the base64encode function. When processing a specially crafted plist file, the function fails to properly validate the length of input data or verify array boundaries before attempting to read memory locations. This allows an attacker to construct a plist file containing malicious base64 data that exceeds expected buffer sizes or contains malformed structures. The out-of-bounds read occurs during the encoding process when the function attempts to access memory addresses that fall outside the allocated buffer boundaries, potentially leading to information disclosure or system instability. This flaw aligns with CWE-129, which describes improper validation of array indices, and represents a common class of memory safety vulnerabilities that can escalate to more serious security implications.
The operational impact of CVE-2017-6437 extends beyond simple denial of service, as it can be leveraged in broader attack scenarios within the mobile device ecosystem. Local users with access to the system can exploit this vulnerability to disrupt normal operations of applications that depend on libplist for property list processing, including mobile device management tools, backup utilities, and development environments. The vulnerability particularly affects systems that process untrusted plist files from external sources, such as iOS device synchronization software, mobile device management platforms, and application deployment tools that utilize libplist for configuration handling. Attackers could potentially use this flaw to gain information about system memory layout or cause application crashes that could be exploited further in combination with other vulnerabilities. This vulnerability maps to ATT&CK technique T1059.007 for execution through scripting and T1566.001 for initial access through malicious files, demonstrating its potential for broader exploitation within mobile device attack surfaces.
Mitigation strategies for CVE-2017-6437 should focus on immediate patching of the libplist library to version 1.13 or later, which contains the necessary bounds checking fixes. System administrators should implement strict input validation for all plist files processed by applications that utilize libplist, particularly those handling external or user-provided data. Network segmentation and privilege separation can help limit the potential impact of exploitation, while monitoring systems should be configured to detect unusual application behavior or crashes that may indicate exploitation attempts. Organizations should also conduct thorough vulnerability assessments of their mobile device management systems and development environments to identify all components that depend on the affected library. The fix implemented in the patched version addresses the root cause by introducing proper bounds checking and input validation within the base64encode function, ensuring that all array accesses are validated against allocated buffer sizes before memory operations occur. Security hardening measures such as address space layout randomization and stack canaries can provide additional defense-in-depth protection against potential exploitation attempts.