CVE-2015-8923 in libarchive
Summary
by MITRE
The process_extra function in libarchive before 3.2.0 uses the size field and a signed number in an offset, which allows remote attackers to cause a denial of service (crash) via a crafted zip file.
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Analysis
by VulDB Data Team • 09/19/2022
The vulnerability identified as CVE-2015-8923 represents a critical denial of service flaw within the libarchive library version 3.2.0 and earlier. This issue specifically affects the process_extra function which handles processing of extra fields in zip file archives. The vulnerability arises from improper handling of size fields and signed offset calculations, creating a condition where maliciously crafted zip files can trigger unexpected behavior in the archive processing routine.
The technical implementation of this vulnerability stems from the manipulation of signed integer arithmetic within the offset calculations used during zip file processing. When the process_extra function encounters a crafted zip file with manipulated size fields, the signed number calculations can produce unexpected results that lead to buffer overflows or invalid memory access patterns. This occurs because the library fails to properly validate the size parameters before performing arithmetic operations on them, allowing attackers to control the offset values used in memory operations.
From an operational perspective, this vulnerability presents significant risks for systems that process untrusted zip files, particularly in web applications, email servers, and file processing services. The remote exploitation capability means that attackers can trigger the denial of service condition without requiring local access or authentication. Systems utilizing libarchive for decompressing zip archives become vulnerable to crashes that can disrupt service availability, potentially leading to cascading failures in larger networked environments where zip file processing is a common operation.
The impact of this vulnerability extends beyond simple service disruption, as it can be leveraged in broader attack chains within the ATT&CK framework under the T1499.004 technique for network denial of service. The vulnerability's location within the core processing logic of libarchive makes it particularly dangerous, as this library is widely used across numerous operating systems and applications for archive handling. Organizations implementing security controls should consider this vulnerability as part of their broader application security posture, particularly in environments where zip file processing is common. The CWE classification for this issue falls under CWE-191, Integer Underflow (Wrap or Wraparound), which specifically addresses the improper handling of signed integer arithmetic that can lead to unexpected behavior in offset calculations.
Mitigation strategies for CVE-2015-8923 primarily involve upgrading to libarchive version 3.2.0 or later, where the vulnerability has been addressed through proper input validation and integer overflow protection mechanisms. Organizations should also implement additional defensive measures such as input sanitization for zip file processing, rate limiting on archive processing operations, and network segmentation to limit the potential impact of successful exploitation attempts. Security monitoring should include detection of unusual patterns in zip file processing that might indicate attempts to exploit this vulnerability, particularly in systems that handle high volumes of user-uploaded archives.