CVE-2018-20252 in WinRar
Summary
by MITRE
There is an out-of-bounds writes vulnerability during parsing of crafted ACE and RAR archive formats. Successful exploitation could lead to arbitrary code execution in the context of the current user.
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Analysis
by VulDB Data Team • 05/08/2020
The vulnerability identified as CVE-2018-20252 represents a critical out-of-bounds write flaw that manifests during the parsing of specially crafted Advanced Compression Engine ace and RAR archive formats. This vulnerability resides within the decompression and parsing logic of archive handling libraries, where improper bounds checking fails to validate the size and structure of archive metadata. The flaw specifically affects applications that process ace and RAR formatted archives, including various media players, file extraction utilities, and archive management tools that rely on vulnerable decompression libraries. The vulnerability is classified under CWE-787 Out-of-bounds Write, which is a fundamental memory safety issue that occurs when a program writes data past the boundaries of a fixed-length buffer. This type of vulnerability typically arises from inadequate input validation and insufficient boundary checks during the parsing of structured data formats.
The technical exploitation of this vulnerability requires an attacker to craft malicious ace or RAR archive files that contain malformed metadata structures designed to trigger the out-of-bounds write condition. When a vulnerable application processes these crafted archives, the parsing routine fails to properly validate the archive headers and metadata, leading to memory corruption that can be leveraged to execute arbitrary code within the context of the current user. The attack vector typically involves user interaction through the opening or extraction of the malicious archive file, making it particularly dangerous in environments where users frequently handle third-party files. The vulnerability does not require administrative privileges for exploitation, as the code execution occurs within the user context, but it can potentially be escalated through additional attack chains. The out-of-bounds write condition creates memory corruption that can overwrite adjacent memory locations, potentially allowing an attacker to manipulate program execution flow through techniques such as return-oriented programming or function pointer overwrites.
The operational impact of CVE-2018-20252 extends across multiple attack surfaces where ace and RAR archive processing occurs, including media players that support these formats, file sharing platforms, and enterprise document management systems. This vulnerability poses significant risk to organizations as it can be exploited through social engineering campaigns targeting users to open malicious archives, or through automated attacks in environments where these archive formats are processed without proper user interaction. The vulnerability is particularly concerning in enterprise environments where users may inadvertently download and open compromised archives from untrusted sources, potentially leading to full system compromise. According to ATT&CK framework, this vulnerability maps to T1059 Command and Scripting Interpreter and T1203 Exploitation for Client Execution, as it enables adversaries to execute malicious code on victim systems through legitimate archive processing applications. The vulnerability's impact is amplified by the widespread use of ace and RAR formats in both personal and enterprise computing environments, making it a preferred target for attackers seeking to establish persistent access or escalate privileges.
Mitigation strategies for CVE-2018-20252 should focus on immediate patching of affected software components, particularly those handling ace and RAR archive formats. System administrators should implement strict file validation policies that scan and quarantine suspicious archive files before processing, while also ensuring that applications are configured to disable automatic extraction of archives from untrusted sources. Network-level protections can include implementing content filtering solutions that block or quarantine ace and RAR files from potentially malicious sources, and deploying application whitelisting policies that restrict execution of known vulnerable applications. Additionally, users should be educated about the risks of opening archives from unknown sources, and organizations should establish secure file handling procedures that include thorough malware scanning of all archive files before processing. The vulnerability also underscores the importance of maintaining up-to-date security patches for all archive processing libraries and applications, as well as implementing memory safety features such as stack canaries and address space layout randomization to make exploitation more difficult. Organizations should conduct regular vulnerability assessments to identify and remediate similar memory safety issues in their software ecosystems, particularly focusing on applications that process structured data formats.