CVE-2017-17969 in 7-zip
Summary
by MITRE
Heap-based buffer overflow in the NCompress::NShrink::CDecoder::CodeReal method in 7-Zip before 18.00 and p7zip allows remote attackers to cause a denial of service (out-of-bounds write) or potentially execute arbitrary code via a crafted ZIP archive.
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Analysis
by VulDB Data Team • 01/10/2025
The heap-based buffer overflow vulnerability identified as CVE-2017-17969 resides within the NCompress::NShrink::CDecoder::CodeReal method of 7-Zip versions prior to 18.00 and the corresponding p7zip implementation. This flaw represents a critical security weakness that manifests when processing specially crafted ZIP archive files, potentially enabling remote attackers to execute arbitrary code or induce denial of service conditions through out-of-bounds write operations. The vulnerability operates at the compression and decompression layer of the software, specifically targeting the decompression algorithm used for handling shrink compression format files.
The technical flaw stems from inadequate input validation and bounds checking within the decompression routine that processes compressed data streams. When the affected 7-Zip versions encounter a malformed ZIP archive containing maliciously constructed shrink compression data, the CDecoder::CodeReal method fails to properly verify buffer boundaries during decompression operations. This deficiency allows attackers to manipulate the decompression process such that data is written beyond the allocated heap memory boundaries, creating opportunities for memory corruption that can be exploited to gain control over the executing process. The vulnerability specifically affects the decompression of files using the shrink compression algorithm, which is a legacy compression method that 7-Zip supports for compatibility purposes.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to encompass potential remote code execution capabilities. An attacker who successfully crafts a malicious ZIP archive can trigger the buffer overflow condition when a victim attempts to extract or process the archive using vulnerable 7-Zip software. The out-of-bounds write operations can corrupt adjacent memory regions, potentially leading to stack corruption, heap corruption, or other memory management issues that may be leveraged to execute arbitrary code with the privileges of the user running the vulnerable software. This makes the vulnerability particularly dangerous in environments where users might unknowingly process untrusted archive files, such as in email attachments, file sharing systems, or web applications that handle user-uploaded content.
The vulnerability aligns with CWE-121, heap-based buffer overflow, and demonstrates characteristics consistent with the attack patterns documented in the MITRE ATT&CK framework under the T1059.007 technique for command and script interpreter execution. Organizations utilizing vulnerable 7-Zip versions face significant risk when processing untrusted archive files, as the attack surface includes any application or system component that relies on 7-Zip's decompression capabilities. The vulnerability's exploitation potential is heightened in environments where automatic decompression occurs, such as email clients or file managers that automatically extract archive contents upon user interaction. Security practitioners should note that the issue affects not only the standalone 7-Zip application but also any software that incorporates p7zip libraries, making it a widespread concern across numerous applications that depend on this compression library.
Mitigation strategies for CVE-2017-17969 primarily focus on upgrading to 7-Zip version 18.00 or later, which includes proper bounds checking and input validation mechanisms. Organizations should also implement restrictive file processing policies that prevent automatic decompression of untrusted archives and employ content filtering systems that can detect and block known malicious archive patterns. Network administrators should consider implementing sandboxed environments for processing potentially malicious files and deploy intrusion detection systems that can identify exploitation attempts. Additionally, regular security assessments should verify that all systems using 7-Zip or p7zip libraries are updated to patched versions, as the vulnerability remains exploitable in older software releases and continues to pose risk in legacy environments where upgrades may not be immediately possible.