CVE-2015-7696 in UnZip
Summary
by MITRE
Info-ZIP UnZip 6.0 allows remote attackers to cause a denial of service (heap-based buffer over-read and application crash) or possibly execute arbitrary code via a crafted password-protected ZIP archive, possibly related to an Extra-Field size value.
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Analysis
by VulDB Data Team • 06/25/2022
The vulnerability identified as CVE-2015-7696 affects Info-ZIP UnZip version 6.0 and represents a critical heap-based buffer over-read condition that can lead to denial of service or arbitrary code execution. This flaw manifests when processing password-protected ZIP archives containing specially crafted Extra-Field size values that exceed expected boundaries. The vulnerability resides in the decompression logic where UnZip fails to properly validate the size parameters of Extra Fields within the ZIP archive structure, creating a scenario where memory access occurs beyond allocated buffer boundaries.
The technical implementation of this vulnerability involves the manipulation of ZIP archive metadata where an attacker crafts a malicious archive with an inflated Extra-Field size value. When UnZip attempts to parse this malformed structure, it allocates memory based on the inflated size value but subsequently reads beyond the allocated buffer limits during the decompression process. This heap-based buffer over-read creates unpredictable memory access patterns that can corrupt adjacent memory regions and ultimately result in application crashes or more severe consequences. The vulnerability is classified under CWE-125 as an out-of-bounds read condition, which directly impacts memory safety and application stability.
From an operational perspective, this vulnerability presents significant risks to systems that process untrusted ZIP archives, particularly those deployed in email systems, file sharing platforms, or automated processing environments. Attackers can exploit this weakness by crafting malicious ZIP files that, when opened by vulnerable UnZip versions, will trigger the buffer over-read condition. The potential for arbitrary code execution makes this vulnerability particularly dangerous in environments where UnZip is used to process files from untrusted sources without proper validation. The attack vector is remote and requires no special privileges, making it accessible to any attacker who can deliver a malicious ZIP file to a target system.
The impact of CVE-2015-7696 extends beyond simple denial of service as the buffer over-read condition can potentially be leveraged for more sophisticated attacks. When memory corruption occurs during the heap-based buffer over-read, attackers may be able to manipulate program execution flow through carefully crafted inputs that overwrite critical memory locations. This aligns with ATT&CK technique T1059.007 for command and scripting interpreter and demonstrates how memory corruption vulnerabilities can serve as initial access vectors for more complex attack chains. The vulnerability affects systems across multiple operating environments where Info-ZIP UnZip is installed, including Unix-like systems and Windows platforms that utilize the UnZip utility.
Mitigation strategies for CVE-2015-7696 should prioritize immediate patching of affected UnZip installations to version 6.0.1 or later, which contains the necessary fixes for the Extra-Field size validation logic. Organizations should implement robust input validation procedures for all ZIP archive processing activities, including the deployment of automated scanning tools that can identify and quarantine suspicious archive files before they are processed. Network-level protections such as content filtering and sandboxing mechanisms can provide additional layers of defense against exploitation attempts. System administrators should also consider disabling automatic extraction of ZIP archives in high-risk environments and implementing strict access controls for systems that process untrusted file inputs. The vulnerability serves as a reminder of the importance of proper memory management and input validation in archive processing utilities, as highlighted in industry best practices for secure software development and the principles outlined in the OWASP Top Ten security framework.