CVE-2017-12424 in shadow
Summary
by MITRE
In shadow before 4.5, the newusers tool could be made to manipulate internal data structures in ways unintended by the authors. Malformed input may lead to crashes (with a buffer overflow or other memory corruption) or other unspecified behaviors. This crosses a privilege boundary in, for example, certain web-hosting environments in which a Control Panel allows an unprivileged user account to create subaccounts.
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Analysis
by VulDB Data Team • 12/14/2022
The vulnerability identified as CVE-2017-12424 affects the shadow package version 4.5 and earlier, specifically targeting the newusers tool which is commonly used for batch creation of user accounts. This flaw represents a critical security issue that arises from insufficient input validation within the tool's internal data processing mechanisms. The vulnerability manifests when the newusers utility encounters malformed input data that causes it to manipulate internal memory structures beyond their intended boundaries. Such manipulation can result in unpredictable system behavior ranging from application crashes due to buffer overflows to more subtle memory corruption issues that may not immediately manifest but could lead to system instability or potential exploitation.
The technical nature of this vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-787, which covers out-of-bounds write operations. The flaw occurs at the intersection of privilege management and input processing, where the tool fails to properly sanitize user-supplied data before processing it within internal data structures. When unprivileged users provide malformed input through the newusers utility, the system's privilege separation mechanisms are effectively bypassed, creating a scenario where attackers can potentially exploit the tool's behavior to cause system-wide disruptions. This particular vulnerability is especially concerning in web hosting environments where control panels allow unprivileged users to create subaccounts, as it creates an attack surface that can be leveraged to compromise the hosting infrastructure.
The operational impact of CVE-2017-12424 extends beyond simple system crashes to potentially enable more sophisticated attacks through the exploitation of memory corruption vulnerabilities. In web hosting contexts, this vulnerability could allow attackers to cause denial of service conditions that affect multiple user accounts or potentially escalate privileges within the hosting environment. The vulnerability's cross-privilege boundary nature means that it can be exploited by users who normally lack elevated permissions to cause disruptions that affect system stability and potentially compromise other users' accounts. Attackers could leverage this flaw to create persistent disruptions or, in more sophisticated scenarios, to establish footholds within hosting environments where multiple users share system resources. The unspecified behaviors mentioned in the original description indicate that the vulnerability may enable additional attack vectors beyond simple crashes, potentially including arbitrary code execution or privilege escalation.
Mitigation strategies for this vulnerability should focus on immediate patching of the shadow package to version 4.5 or later, where the input validation issues have been addressed. System administrators should also implement strict input validation at the control panel level to prevent malformed data from reaching the newusers utility. Additional security measures include restricting access to the newusers tool through proper privilege controls and implementing monitoring for unusual patterns of user account creation that might indicate exploitation attempts. Organizations should also consider implementing application whitelisting controls to prevent execution of untrusted binaries that might attempt to exploit similar vulnerabilities. The ATT&CK framework's T1068 technique for exploit for privilege escalation and T1489 for input validation bypasses can be used to detect and prevent exploitation attempts. Regular security auditing of system tools and their input handling mechanisms remains crucial for identifying similar vulnerabilities that could exist in other utilities within the system's attack surface.