CVE-2017-5976 in ZZIPlib
Summary
by MITRE
Heap-based buffer overflow in the zzip_mem_entry_extra_block function in memdisk.c in zziplib 0.13.62 allows remote attackers to cause a denial of service (crash) via a crafted ZIP file.
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Analysis
by VulDB Data Team • 07/10/2025
The heap-based buffer overflow vulnerability identified as CVE-2017-5976 exists within the zziplib library version 0.13.62, specifically within the zzip_mem_entry_extra_block function located in the memdisk.c source file. This vulnerability represents a critical security flaw that can be exploited by remote attackers to execute a denial of service attack against systems utilizing this library. The flaw occurs when the library processes malformed ZIP archive files, particularly those containing crafted extra data blocks that exceed expected buffer boundaries during memory allocation and data copying operations.
The technical implementation of this vulnerability stems from inadequate input validation and buffer size checking within the memory handling routines of zziplib. When the zzip_mem_entry_extra_block function processes extra data blocks from ZIP file entries, it fails to properly validate the length of the extra data before attempting to copy it into a heap-allocated buffer. This oversight allows attackers to craft ZIP files containing oversized extra data fields that overflow the allocated buffer space, potentially corrupting adjacent memory regions and causing the application to crash or behave unpredictably. The vulnerability specifically manifests during the parsing of ZIP archive metadata, particularly when handling the extra field data that accompanies file entries within ZIP archives.
From an operational perspective, this vulnerability poses significant risks to systems that rely on zziplib for ZIP file processing, including web applications, file processing services, and archive management tools. The remote exploitation capability means that attackers can trigger the vulnerability without requiring local access to the target system, making it particularly dangerous in networked environments. Systems utilizing vulnerable versions of zziplib may experience complete service disruption when processing maliciously crafted ZIP files, leading to denial of service conditions that can impact availability and potentially provide attackers with opportunities for further exploitation. The crash condition typically occurs during normal ZIP file parsing operations, making it difficult to distinguish between legitimate and malicious files until the vulnerability is triggered.
The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent heap memory. This flaw also maps to ATT&CK technique T1203, which covers legitimate programs that are used to perform malicious actions, in this case through the exploitation of memory corruption vulnerabilities in commonly used libraries. Organizations using affected systems should prioritize immediate patching of their zziplib installations to address this vulnerability. The recommended mitigation strategy involves upgrading to a patched version of zziplib that implements proper buffer size validation and input sanitization for extra data blocks within ZIP archives. Additionally, implementing defensive measures such as input validation at the application level and restricting ZIP file processing to trusted sources can provide additional protection layers against exploitation attempts.