CVE-2021-32840 is a high-severity vulnerability affecting SharpZipLib, a widely used library for handling ZIP, GZIP, TAR, and BZIP2 formats. The vulnerability arises from improper handling of TAR file entries, where an entry such as `../evil.txt` could be extracted to the parent directory of the target destination folder. This flaw could lead to arbitrary file writes, potentially resulting in code execution. The vulnerability was patched in version 1.3.3 of the library.
The Common Vulnerability Scoring System (CVSS) score for CVE-2021-32840 is 7.3, which indicates a high severity level. This score reflects the local attack vector and low complexity required for exploitation, meaning that an attacker could exploit this vulnerability without needing elevated privileges or user interaction. The risk to organizations includes unauthorized access to sensitive files and potential system compromise.
As of now, no known exploits have been publicly reported, but the nature of this vulnerability requires immediate attention. Organizations utilizing SharpZipLib should prioritize applying the relevant patches to version 1.3.3 or above to mitigate any associated risks. Given the potential for exploitation, organizations should consider this vulnerability a high priority for their security remediation efforts.
Organizations should prioritize patching immediately to ensure their systems remain secure against this vulnerability and similar threats.
Vulnerability Details
The vulnerability identified as CVE-2021-32840 is specifically tied to SharpZipLib, which is utilized for various file compression and decompression tasks. The vulnerability allows an attacker to exploit the path traversal flaw present in TAR file handling. The official CVE description states that this vulnerability allows arbitrary file writes that may lead to code execution. It is classified under CWE-22 (Improper Limitation of a Pathname to a Restricted Directory).
The CVSS score provided by NVD is 9.8, classifying it as critical. This high score indicates that the vulnerability poses a significant threat if exploited. The attack vector is classified as network-based with low complexity, requiring no privileges or user interaction. This means that an attacker can potentially exploit this vulnerability remotely without needing to authenticate or interact with a user.
The vulnerability affects versions of SharpZipLib prior to 1.3.3. The disclosure date was January 26, 2022, and it has since been modified to reflect ongoing assessments. Organizations utilizing this library should be aware of the necessary upgrades and the critical nature of this vulnerability.
Technical Analysis
The root cause of CVE-2021-32840 is the improper handling of TAR file entries within the SharpZipLib library. Specifically, the library does not adequately validate the paths in TAR file entries, allowing for path traversal attacks. An attacker can craft a TAR file containing an entry that points to a parent directory, which would allow them to write files outside the intended extraction directory.
The attack vector for this vulnerability is local, meaning that an attacker must have access to the system where the extraction takes place. The attack complexity is low, and no privileges are required to exploit this vulnerability, making it easier for attackers to execute. Furthermore, there is no user interaction required for successful exploitation, increasing the risk of silent attacks.
In terms of impacts, the confidentiality impact is classified as low, while the integrity impact is high. This indicates that while sensitive information may not be immediately exposed, the potential for unauthorized modifications to files or code execution is significant. The availability impact is low, meaning that system availability is not directly threatened by this vulnerability.
Risk & Impact Analysis
The real-world risk associated with CVE-2021-32840 is significant, particularly for organizations that rely on SharpZipLib for file handling. The ability to execute arbitrary file writes can lead to unauthorized access or modifications of critical files, which can compromise system integrity and lead to further attacks. Given the library's common usage, the potential blast radius is considerable.
With an EPS score of 0.015, which places it in the 81.4 percentile, there is a low probability of exploitation based on current data. However, this should not diminish the urgency to address the vulnerability. Organizations should assess their deployment of SharpZipLib and prioritize remediation efforts to mitigate any potential exploitation.
In conclusion, organizations must take the necessary steps to patch this vulnerability immediately to safeguard their systems and data from potential exploitation.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The vulnerability affects all versions of SharpZipLib prior to version 1.3.3. Organizations using these versions are strongly advised to upgrade to the patched version to eliminate the risk associated with this vulnerability.
Mitigation & Remediation
To mitigate the risk associated with CVE-2021-32840, organizations should upgrade to SharpZipLib version 1.3.3 or later. This version includes the necessary patches to address the vulnerability. If immediate upgrading is not feasible, organizations should consider implementing workarounds such as restricting file extraction paths and conducting thorough reviews of compressed files before extraction.
Additionally, organizations should implement configuration hardening by limiting the permissions of users who can extract files and monitor file extraction activities closely. Regular vulnerability assessments and penetration testing can help identify potential weaknesses in file handling mechanisms.
For more detailed guidance, organizations can refer to resources on penetration testing and application security best practices.
Detection Guidance
Organizations should monitor logs for unusual file extraction activities, especially those involving TAR files. Additionally, they should look for behavioral anomalies, such as unauthorized file writes or modifications in critical directories.
Network signatures should be established to detect any abnormal use of the SharpZipLib library in application logs. Regular reviews of file handling practices and access controls can help mitigate risks associated with this vulnerability.
AppSecure Threat Intelligence Insight
CVE-2021-32840 represents a critical vulnerability in a widely adopted library, underscoring the importance of maintaining up-to-date software components. Organizations should ensure their libraries are regularly reviewed and updated to prevent similar vulnerabilities from affecting their systems.
This vulnerability highlights a broader trend toward path traversal vulnerabilities in software libraries, emphasizing the need for rigorous input validation and path sanitization in file processing routines. Security teams should adopt a proactive stance on vulnerability management, ensuring continuous monitoring and assessment of their software supply chain.
For further reading on best practices in application security, organizations can explore topics related to penetration testing methodology, vulnerability management programs, and API security testing to strengthen their defenses against future vulnerabilities.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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