CVE-2018-20250
WinRAR Absolute Path Traversal Vulnerability
Description
CVE-2018-20250 is a HIGH absolute path traversal vulnerability affecting RARLAB WinRAR, carrying a CVSS 3.1 score of 7.8. WinRAR Absolute Path Traversal vulnerability leads to Remote Code Execution Affected products include Rarlab Winrar (<= 5.61). This CVE is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog with a remediation deadline of 2022-08-15. CISA's KEV catalog confirms ransomware association for this vulnerability. With an EPSS score of 0.93462 (99.82th percentile), this vulnerability demonstrates significant real-world exploitation activity and should be prioritized for immediate remediation.
KEV Information
CVSS Score
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| rarlab | winrar | <= 5.61 |
Multiple CVSS Assessments
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
References
- http://packetstormsecurity.com/files/152618/RARLAB-WinRAR-ACE-Format-Input-Validation-Remote-Code-Execution.html(Exploit, Third Party Advisory, VDB Entry)
- http://www.rapid7.com/db/modules/exploit/windows/fileformat/winrar_ace(Third Party Advisory)
- http://www.securityfocus.com/bid/106948(Broken Link, Third Party Advisory, VDB Entry)
- https://github.com/blau72/CVE-2018-20250-WinRAR-ACE(Exploit, Third Party Advisory)
- https://research.checkpoint.com/extracting-code-execution-from-winrar/(Exploit, Press/Media Coverage, Third Party Advisory)
- https://www.exploit-db.com/exploits/46552/(Exploit, Third Party Advisory, VDB Entry)
- https://www.exploit-db.com/exploits/46756/(Exploit, Third Party Advisory, VDB Entry)
- https://www.win-rar.com/whatsnew.html(Release Notes)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-20250(US Government Resource)
Weakness Type
CWE-36: Absolute Path Traversal
CVE-2018-20250 is classified under CWE-36 — Absolute Path Traversal. Absolute Path Traversal is a vulnerability that occurs when software accepts user input containing absolute file paths (paths that start from the filesystem root) without properly validating that the specified path is within an authorized directory. Unlike relative path traversal which uses sequences like "../" to navigate upward, absolute path traversal allows attackers to directly specify complete paths such as "/etc/passwd" on Unix systems or "C:\Windows\system32\config\SAM" on Windows. This vulnerability bypasses directory restrictions by ignoring any base directory the application intends to use, giving attackers direct access to any file readable by the application process.
In the context of RARLAB WinRAR, this weakness is particularly concerning because Absolute path traversal vulnerabilities allow attackers to bypass directory restrictions entirely by specifying complete filesystem paths. This grants immediate access to sensitive system files including /etc/passwd (user accounts), /etc/shadow (password hashes on misconfigured systems), application configuration files, database credentials, private keys, and source code. The attack is particularly dangerous because it requires no directory traversal sequences that security filters might detect, making it easier to bypass naive security controls. Organizations using affected versions should understand that this vulnerability class has historically enabled severe compromises across enterprise environments.
Impact Analysis
CVE-2018-20250 carries a CVSS 3.1 score of 7.8 (HIGH) with Unchanged Scope.
Confidentiality (HIGH): Successful exploitation grants the attacker extensive access to sensitive data processed by RARLAB WinRAR, including configuration files, credentials, and potentially data from connected systems.
Integrity (HIGH): Attackers can modify critical system files, install backdoors, alter configurations, or deploy malware on affected systems running RARLAB WinRAR.
Availability (HIGH): Complete disruption of the affected service or system is possible, including denial of service, system crashes, or rendering the product inoperable.
Scope Unchanged: The vulnerability's scope is Unchanged (U), meaning exploitation is contained within the vulnerable component. The impact, while significant, is limited to the RARLAB WinRAR environment itself.
With an EPSS score of 0.93462 (99.82th percentile), this vulnerability ranks among the most likely to be exploited in real-world attacks, underscoring the urgency of remediation.
Exploit Maturity
CVE-2018-20250 has confirmed active exploitation in the wild and is listed in CISA's Known Exploited Vulnerabilities catalog.
Exploit status: This vulnerability has been actively exploited, as confirmed by its inclusion in the KEV catalog. The EPSS score of 0.93462 (99.82th percentile) places it among the most exploited vulnerabilities tracked.
Ransomware association: CISA's KEV catalog confirms a known association between CVE-2018-20250 and ransomware campaigns. Threat actors have leveraged this vulnerability as part of ransomware attack chains for initial access or lateral movement.
Public exploits: Exploit code is publicly available, including references at packetstormsecurity.com and github.com. The availability of public exploit code significantly lowers the barrier to exploitation.
KEV deadline: CISA required federal agencies to remediate this vulnerability by 2022-08-15. All organizations should treat this deadline as a strong recommendation for their own remediation timelines.
Remediation
- Apply vendor patches immediately. Apply updates per vendor instructions.
- Verify affected product versions in your environment. Identify all instances of RARLAB WinRAR in your infrastructure (affected versions: Rarlab Winrar (<= 5.61)). Use asset inventory and vulnerability scanning tools to ensure no instances are missed.
- Implement interim mitigations if patching is delayed. If immediate patching is not feasible, apply network-level controls such as restricting access to the affected component, enabling enhanced logging, and monitoring for indicators of compromise.
- Scan for signs of prior exploitation. Given the confirmed active exploitation of this vulnerability, review system logs and security monitoring data for evidence of compromise. Conduct a thorough investigation if any suspicious activity is detected.
- Update detection signatures and monitoring rules. Ensure intrusion detection and prevention systems, endpoint detection tools, and SIEM rules are updated to detect exploitation attempts targeting CVE-2018-20250.
- Conduct a post-remediation review. After patching, verify the fix is effective and document the remediation actions taken. Update your vulnerability management records and assess whether any additional hardening measures are warranted.
Technical Details
CVE-2018-20250 is a HIGH-severity vulnerability in RARLAB WinRAR that can be exploited locally, typically requiring a user to open a malicious file or execute a malicious application. The attack complexity is low, meaning no specialized conditions or preparation are required beyond the attack prerequisites. No prior authentication or privileges are needed to initiate the attack. User interaction is required, meaning a victim must perform an action such as opening a file, clicking a link, or visiting a website for exploitation to succeed.
Technical mechanism: WinRAR Absolute Path Traversal vulnerability leads to Remote Code Execution The underlying flaw relates to absolute path traversal, where Absolute Path Traversal is a vulnerability that occurs when software accepts user input containing absolute file paths (paths that start from the filesystem root) without properly validating that the specified path is within an authorized directory. Unlike relative path traversal which uses sequences like "../" to navigate upward, absolute path traversal allows attackers to directly specify complete paths such as "/etc/passwd" on Unix systems or "C:\Windows\system32\config\SAM" on Windows.
CVSS 3.1 vector analysis: The vector reflects an Attack Vector of LOCAL, Attack Complexity of LOW, Privileges Required of NONE, User Interaction of REQUIRED, Scope UNCHANGED, and impact ratings of HIGH/HIGH/HIGH for Confidentiality/Integrity/Availability respectively. The Unchanged scope means impact is contained within the vulnerable component itself.
Frequently Asked Questions
What is CVE-2018-20250?
CVE-2018-20250 is a HIGH-severity vulnerability (CVSS 7.8) in RARLAB WinRAR that winRAR Absolute Path Traversal vulnerability leads to Remote Code Execution. It is listed in CISA's Known Exploited Vulnerabilities catalog, confirming real-world exploitation. This vulnerability has been associated with ransomware campaigns.
Which products are affected by CVE-2018-20250?
The affected products include Rarlab Winrar (<= 5.61). Organizations running any of these versions should verify their exposure and prioritize remediation. Check vendor advisories for the complete and most current list of affected versions.
How do I fix CVE-2018-20250?
Apply updates per vendor instructions. Ensure all affected instances of RARLAB WinRAR are identified using vulnerability scanning and asset management tools. If immediate patching is not possible, implement network-level mitigations and enhanced monitoring. After patching, verify the fix and scan for indicators of prior compromise.
How severe is CVE-2018-20250?
CVE-2018-20250 is rated HIGH with a CVSS 3.1 score of 7.8. Its EPSS score of 0.93462 places it in the 99.82th percentile for exploitation likelihood. The vulnerability has confirmed active exploitation in the wild and is associated with ransomware campaigns, was required to be remediated by federal agencies by 2022-08-15 per CISA's KEV directive.
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