CVE-2018-6540 in ZZIPlib
Summary
by MITRE
In ZZIPlib 0.13.67, there is a bus error caused by loading of a misaligned address in the zzip_disk_findfirst function of zzip/mmapped.c. Remote attackers could leverage this vulnerability to cause a denial of service via a crafted zip file.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 07/10/2025
The vulnerability identified as CVE-2018-6540 affects ZZIPlib version 0.13.67, a library used for reading zip archives in memory-mapped mode. This flaw manifests as a bus error during the execution of the zzip_disk_findfirst function located within the zzip/mmapped.c source file. The root cause stems from improper handling of memory alignment when processing zip file structures, specifically when the library attempts to access memory addresses that are not properly aligned for the target architecture. This misalignment occurs during the parsing of zip file headers and directory entries, where the library assumes certain memory alignment properties that may not hold true for all input data, particularly when dealing with crafted malicious inputs.
The technical implementation of this vulnerability involves the library's memory management approach when utilizing memory mapping techniques for zip file processing. When ZZIPlib encounters a zip archive, it employs memory mapping to access file contents directly from memory rather than using traditional file I/O operations. The zzip_disk_findfirst function specifically handles the initial search for files within a zip archive by examining directory structures. During this process, the function accesses memory addresses that are not properly aligned according to the processor's requirements for efficient memory access. This misalignment triggers a bus error on architectures that strictly enforce memory alignment, such as ARM and certain RISC processors, causing the application to crash and resulting in a denial of service condition.
From an operational perspective, this vulnerability represents a significant security concern for systems that utilize ZZIPlib for processing untrusted zip archives. Remote attackers can exploit this weakness by crafting specially formatted zip files that trigger the misaligned memory access during the zzip_disk_findfirst function execution. The impact extends beyond simple service disruption as this vulnerability can be leveraged in broader attack scenarios where denial of service is used as a component of more sophisticated attacks. The vulnerability affects any application that depends on ZZIPlib for zip file processing, including web applications, file processing utilities, and archive management systems that handle user-provided content without proper validation.
The security implications of CVE-2018-6540 align with CWE-121, which addresses stack-based buffer overflow conditions, and CWE-123, which covers dangerous use of strcpy. The vulnerability demonstrates poor memory alignment handling practices that can lead to system instability and potential information disclosure. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to network denial of service, where attackers can disrupt services by causing application crashes. The vulnerability also relates to T1595.001 for reconnaissance activities where attackers might analyze system behavior to identify exploitable conditions.
Mitigation strategies for this vulnerability should focus on immediate patching of ZZIPlib to version 0.13.68 or later, which contains the necessary fixes for proper memory alignment handling. System administrators should implement input validation and sanitization for all zip file processing operations, particularly when handling user-provided content. Additionally, applications using ZZIPlib should implement proper error handling and recovery mechanisms to prevent complete service disruption. Network-level defenses including intrusion detection systems can be configured to monitor for suspicious zip file patterns that might indicate exploitation attempts. The fix typically involves ensuring that memory access operations properly account for alignment requirements and implement proper bounds checking during zip file parsing operations.