CVE-2014-9984 in C Library
Summary
by MITRE
nscd in the GNU C Library (aka glibc or libc6) before version 2.20 does not correctly compute the size of an internal buffer when processing netgroup requests, possibly leading to an nscd daemon crash or code execution as the user running nscd.
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Analysis
by VulDB Data Team • 12/08/2022
The vulnerability identified as CVE-2014-9984 resides within the name service caching daemon nscd component of the GNU C Library, commonly known as glibc or libc6. This flaw specifically manifests when the nscd daemon processes netgroup requests, which are used to define network groups for access control and authentication purposes in Unix-like operating systems. The nscd service operates as a background daemon that caches name service lookups to improve system performance by reducing repeated network requests to directory services. The vulnerability affects all versions of glibc prior to version 2.20, making it a widespread issue across numerous Linux distributions and Unix systems that rely on this critical system component for name resolution and user authentication services.
The technical root cause of this vulnerability lies in an incorrect buffer size calculation within the nscd daemon's processing logic for netgroup requests. When nscd receives a netgroup request, it attempts to allocate an internal buffer to store the response data, but due to a miscalculation in determining the appropriate buffer size, the system allocates insufficient memory space. This buffer overflow condition occurs because the daemon does not properly account for the actual size requirements of netgroup data structures when computing memory allocation. The flaw is classified under CWE-122, which specifically addresses heap-based buffer overflow conditions, and represents a classic example of improper input validation leading to memory corruption vulnerabilities. The incorrect buffer size computation creates a scenario where maliciously crafted netgroup requests can trigger memory corruption that may result in unpredictable behavior.
The operational impact of this vulnerability extends beyond simple service disruption to potentially enable remote code execution under specific conditions. When the nscd daemon encounters a malformed netgroup request that triggers the buffer overflow, the system may experience a crash leading to a denial of service condition that affects name resolution services and authentication mechanisms. However, the more serious concern arises when the buffer overflow allows for arbitrary code execution with the privileges of the user running the nscd daemon, typically a system-level account. This privilege escalation capability makes the vulnerability particularly dangerous in environments where nscd is running with elevated permissions, as it could enable attackers to compromise the entire system. The vulnerability aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation', and T1059, covering 'Command and Scripting Interpreter', as successful exploitation could allow attackers to execute arbitrary commands on the compromised system.
Mitigation strategies for CVE-2014-9984 primarily focus on upgrading the affected glibc package to version 2.20 or later, which contains the necessary patches to correct the buffer size calculation logic. System administrators should prioritize patching all affected systems, particularly those running nscd services that are accessible to untrusted networks or users. Additional mitigations include disabling nscd services when they are not required, implementing network segmentation to limit access to nscd ports, and monitoring for suspicious netgroup request patterns that might indicate exploitation attempts. Organizations should also consider implementing intrusion detection systems that can identify malformed netgroup requests and anomalous behavior in nscd processes. The vulnerability demonstrates the critical importance of proper memory management in system services and highlights the need for comprehensive input validation and buffer size calculations in security-critical components. Regular security assessments and vulnerability scanning should include verification of nscd configurations and glibc versions to prevent exploitation of this and similar buffer overflow vulnerabilities.