CVE-2015-8922 in libarchive
Summary
by MITRE
The read_CodersInfo cuntion in archive_read_support_format_7zip.c in libarchive before 3.2.0 allows remote attackers to cause a denial of service (NULL pointer derference and crash) via a crafted 7z file, related to the _7z_folder struct.
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Analysis
by VulDB Data Team • 09/19/2022
The vulnerability identified as CVE-2015-8922 represents a critical denial of service flaw within the libarchive library version 3.1.5 and earlier, specifically affecting the read_CodersInfo function in the archive_read_support_format_7zip.c component. This issue manifests when processing maliciously crafted 7z archive files that contain malformed _7z_folder structures, leading to a NULL pointer dereference condition that ultimately results in application crashes. The vulnerability resides in the archive extraction and parsing logic that handles 7zip format archives, making it particularly dangerous in environments where automated archive processing occurs. The flaw demonstrates a classic lack of proper input validation and error handling within the archive parsing pipeline, where the software fails to adequately validate the structure and content of the 7z file metadata before attempting to dereference pointers that may remain uninitialized or null.
The technical implementation of this vulnerability stems from insufficient bounds checking and validation within the _7z_folder structure parsing logic. When the read_CodersInfo function processes a malformed 7z file, it attempts to access fields within the _7z_folder structure without first verifying that these fields contain valid data or that the structure itself has been properly initialized. This pattern of operation directly violates secure coding principles and creates a predictable crash condition that attackers can exploit consistently. The vulnerability operates at the level of archive format parsing and demonstrates how malformed input can cascade into system stability issues, particularly when the library is used in applications that automatically extract or process archives without proper sanitization. The NULL pointer dereference occurs during the normal execution flow of archive processing, making it difficult to distinguish between legitimate and malicious input without proper validation mechanisms.
The operational impact of CVE-2015-8922 extends beyond simple service disruption to potentially enable more sophisticated attack vectors when combined with other vulnerabilities or in specific deployment scenarios. Systems that rely on libarchive for processing user-uploaded content, automated backup restoration, or file extraction services become particularly vulnerable to this type of denial of service attack. The vulnerability affects a wide range of applications including web servers, file management systems, and content delivery networks that utilize libarchive for archive handling. Attackers can leverage this flaw to repeatedly crash services by simply sending malicious 7z files, potentially leading to resource exhaustion or system instability. This vulnerability aligns with the CWE-476 principle of NULL Pointer Dereference and demonstrates how improper input handling can lead to system instability. The attack surface is particularly broad since 7zip format is widely used across various platforms and applications, making the impact of this vulnerability widespread.
Mitigation strategies for CVE-2015-8922 require immediate patching of affected libarchive installations to version 3.2.0 or later, where the vulnerability has been addressed through improved input validation and null pointer checks. Organizations should implement proper input sanitization procedures for all archive file processing, including validation of file headers and metadata before attempting to parse complex structures. The fix typically involves adding comprehensive checks for pointer validity and structure initialization before dereferencing any pointers within the _7z_folder parsing logic. Additionally, system administrators should consider implementing file type restrictions and content scanning for archive files, particularly those submitted by untrusted sources. The remediation process should include thorough testing of patched libraries to ensure that legitimate archive processing continues to function correctly while preventing the exploitation of this vulnerability. From an operational security perspective, this vulnerability highlights the importance of maintaining up-to-date third-party libraries and implementing robust input validation as core security controls within software applications. The ATT&CK framework categorizes this type of vulnerability under the T1499 category of Network Denial of Service, emphasizing the need for proper input validation and error handling in archive processing components.