CVE-2016-7166 in libarchive
Summary
by MITRE
libarchive before 3.2.0 does not limit the number of recursive decompressions, which allows remote attackers to cause a denial of service (memory consumption and application crash) via a crafted gzip file.
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Analysis
by VulDB Data Team • 09/19/2022
The vulnerability identified as CVE-2016-7166 affects libarchive versions prior to 3.2.0 and represents a critical denial of service flaw that exploits recursive decompression mechanisms within the library. This issue manifests when the library processes specially crafted gzip files that contain nested compressed data structures, leading to unbounded recursive decompression operations. The flaw stems from the absence of proper recursion depth limiting within the decompression routine, allowing attackers to construct malicious archive files that trigger infinite or excessively deep recursive decompression sequences. The vulnerability impacts any application that relies on libarchive for handling compressed files, including file managers, backup utilities, and content extraction tools, making it particularly dangerous in environments where untrusted archives are processed.
The technical implementation of this vulnerability resides in the decompression logic of libarchive's gzip handling code, where the library fails to enforce maximum recursion limits during decompression operations. When a crafted gzip file contains multiple nested compression layers, the decompression routine recursively calls itself without checking the current recursion depth against a predefined threshold. This allows an attacker to create archives with arbitrarily deep nesting levels, causing the decompression process to consume excessive memory resources and eventually leading to application crashes or system resource exhaustion. The flaw operates at the library level rather than at the application layer, meaning that any software utilizing libarchive for decompression purposes becomes vulnerable regardless of the specific implementation details of that software.
The operational impact of CVE-2016-7166 extends beyond simple resource exhaustion to encompass broader system stability and availability concerns. Attackers can leverage this vulnerability to consume system memory rapidly, potentially causing system slowdowns, application crashes, or complete system hangs depending on the target environment. The memory consumption pattern follows a predictable exponential growth curve as recursion depth increases, making it particularly effective for resource exhaustion attacks. In server environments where libarchive is used for processing user-uploaded content, this vulnerability could enable denial of service attacks that render services unavailable to legitimate users. The vulnerability also poses risks in automated processing environments such as content filtering systems, where unbounded recursion could lead to cascading failures across multiple processing threads or processes.
Mitigation strategies for CVE-2016-7166 primarily focus on upgrading to libarchive version 3.2.0 or later, which includes proper recursion depth limiting mechanisms. System administrators should also implement additional protective measures such as setting resource limits on decompression processes, implementing file size restrictions on uploaded archives, and monitoring for unusual memory consumption patterns during decompression operations. Network-level protections can include content filtering systems that scan for suspicious compression patterns and limit the number of nested compression layers permitted in processed files. The vulnerability aligns with CWE-674, which addresses "Uncontrolled Recursion" and falls under ATT&CK technique T1499.001, "File Deletion" and "Resource Hijacking" through denial of service mechanisms. Organizations should also consider implementing sandboxing techniques for archive processing and maintaining regular security updates to prevent exploitation of similar recursion-based vulnerabilities in other libraries and applications.