CVE-2014-9636 in unzip
Summary
by MITRE
unzip 6.0 allows remote attackers to cause a denial of service (out-of-bounds read or write and crash) via an extra field with an uncompressed size smaller than the compressed field size in a zip archive that advertises STORED method compression.
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Analysis
by VulDB Data Team • 04/12/2022
The vulnerability identified as CVE-2014-9636 represents a critical buffer management flaw in the unzip utility version 6.0 that manifests through improper handling of zip archive extra fields. This issue occurs when the unzip utility processes zip files containing extra fields where the uncompressed size is smaller than the compressed field size, creating a scenario where the decompression routine attempts to access memory locations beyond the allocated buffer boundaries. The flaw specifically affects zip archives that advertise the STORED method compression, which is a no-compression method that should theoretically preserve the original data structure without modification.
The technical implementation of this vulnerability stems from inadequate validation of field size parameters during the parsing of zip archive metadata. When unzip encounters an extra field with inconsistent size parameters, the decompression logic fails to properly bounds-check memory operations, leading to out-of-bounds read or write conditions. This memory corruption can result in arbitrary code execution or system crashes, depending on the specific memory access pattern triggered by the malformed data. The vulnerability operates at the application layer and can be exploited remotely through malicious zip archives delivered via web downloads, email attachments, or file sharing platforms, making it particularly dangerous in enterprise environments where users frequently interact with external file sources.
From an operational impact perspective, this vulnerability creates significant risk for organizations relying on unzip for automated file processing or user file extraction. The denial of service condition can disrupt legitimate business operations when critical files become inaccessible due to unzip crashes, while the potential for out-of-bounds writes opens possibilities for privilege escalation or remote code execution in certain environments. The vulnerability affects systems where unzip is used for automated processing of user uploads, file synchronization services, or any scenario where untrusted zip archives are processed without proper validation. This makes it particularly concerning for web applications, cloud storage services, and content delivery networks that handle large volumes of user-generated content.
Security practitioners should implement immediate mitigations including updating to unzip version 6.0 or later where this vulnerability has been patched, deploying input validation controls for zip file processing, and implementing sandboxing mechanisms for file extraction operations. The vulnerability aligns with CWE-129, which addresses insufficient bounds checking, and can be mapped to ATT&CK technique T1203, representing exploitation of software vulnerabilities for privilege escalation. Organizations should also consider implementing network-based intrusion detection systems to monitor for suspicious zip file handling patterns and establish secure file processing protocols that validate archive integrity before decompression. Regular security assessments should include vulnerability scanning for outdated unzip versions and comprehensive testing of file processing pipelines to ensure proper bounds checking and memory management practices are in place.