In Shadow 4.13, it is possible to inject control characters into fields provided to the SUID program chfn (change finger). Although it is not possible to exploit this directly (e.g., adding a new user fails because \n is in the block list), it is possible to misrepresent the /etc/passwd file when viewed. Use of \r manipulations and Unicode characters to work around blocking of the : character make it possible to give the impression that a new user has been added. In other words, an adversary may be able to convince a system administrator to take the system offline (an indirect, social-engineered denial of service) by demonstrating that "cat /etc/passwd" shows a rogue user account.
This vulnerability allows for a misleading representation of user accounts, which could lead to significant administrative confusion. The attack vector is local, requiring low privileges and no user interaction. Organizations running affected versions of Shadow should take this vulnerability seriously, particularly given its potential to indirectly cause service disruptions.
The CVSS score of 3.3 categorizes this vulnerability as low severity, implying that while it may not pose an immediate threat, organizations should still prioritize addressing it during their regular patch cycle.
Organizations should prioritize remediation efforts to prevent any social-engineering attacks that exploit this vulnerability. The potential for misrepresentation of user accounts can undermine system integrity and lead to deeper security issues.
Vulnerability Details
The official CVE description states that this vulnerability allows control character injection into fields for the SUID program chfn. The affected version is Shadow 4.13, which has been modified to address this issue. The vulnerability is classified under CWE-74 and CWE-125, indicating a weakness associated with improper handling of special characters.
With a CVSS score of 3.3, the severity of this vulnerability is considered low. The attack vector is local, meaning it requires access to the system where the vulnerable software is installed. The attack complexity is low, and only low privileges are required to exploit this vulnerability.
The vulnerability was published on April 14, 2023, and has been modified since initial disclosure. Organizations using Shadow 4.13 should consider updating to a patched version to mitigate the risks.
Technical Analysis
The root cause of this vulnerability lies in the handling of control characters within the chfn program. While the direct exploitation of this vulnerability is blocked, the ability to manipulate the output of the /etc/passwd file presents a significant issue. This vulnerability can be exploited locally, requiring the attacker to have low privileges on the system.
The attack complexity is classified as low, as it does not require extensive technical knowledge or skills to execute the manipulation. Furthermore, user interaction is not required, which increases the likelihood of successful exploitation.
Confidentiality impact is rated as none, while integrity impact is rated as low. There is no availability impact associated with this vulnerability, meaning that it does not disrupt system operations directly. However, the potential for social-engineered denial of service remains a concern.
Risk & Impact Analysis
Risk to organizations includes the potential for unauthorized representation of user accounts within the system. This could mislead system administrators into believing that unauthorized accounts have been created, leading to unnecessary administrative actions such as taking the system offline. The indirect denial of service resulting from this misrepresentation poses a significant risk.
Given the low severity of the CVSS score, organizations should address this vulnerability in their priority patch cycle. While it may not be an immediate threat, the potential for misrepresentation in critical user account management processes necessitates prompt remediation.
The exploitation of this vulnerability could lead to a wider blast radius if left unaddressed. Organizations should ensure that their security measures include strict input validation to prevent control character injection in user management processes.
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The only affected version identified is Shadow 4.13. Organizations should ensure that they are using a version that has been patched to mitigate this vulnerability.
Mitigation & Remediation
Organizations should prioritize patching by upgrading to a version that addresses this vulnerability. Regular monitoring of systems for unauthorized changes to user accounts is also recommended. Configuration hardening should be implemented to restrict control character input in user management processes.
For comprehensive security, consider integrating penetration testing into your security strategy to identify similar weaknesses.
Detection Guidance
Organizations should monitor logs for unusual activity related to user account management. Behavioral anomalies, such as unexpected changes to user accounts or attempts to manipulate the /etc/passwd file, should be flagged and investigated. Additionally, implementing network signatures to detect unauthorized access attempts can enhance security.
AppSecure Threat Intelligence Insight
The long-term significance of this vulnerability lies in its potential to affect system integrity through user account misrepresentation. It serves as a reminder for organizations to rigorously validate input in user management systems. Security teams should learn from this incident and bolster their defenses against similar vulnerabilities.
For further insights on vulnerability management, consider the following resources: vulnerability management program design, penetration testing methodology, and the importance of security testing best practices in safeguarding your systems.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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