CVE-2015-5277 in C Library
Summary
by MITRE
The get_contents function in nss_files/files-XXX.c in the Name Service Switch (NSS) in GNU C Library (aka glibc or libc6) before 2.20 might allow local users to cause a denial of service (heap corruption) or gain privileges via a long line in the NSS files database.
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Analysis
by VulDB Data Team • 06/28/2022
The vulnerability identified as CVE-2015-5277 represents a critical heap corruption flaw within the Name Service Switch implementation of the GNU C Library. This issue specifically affects the get_contents function in the nss_files/files-XXX.c component, which handles NSS file database operations. The vulnerability stems from inadequate input validation when processing long lines within NSS configuration files, creating a potential vector for both privilege escalation and denial of service attacks. The flaw exists in glibc versions prior to 2.20, making a substantial portion of Unix-like systems vulnerable to exploitation.
The technical implementation of this vulnerability involves a buffer overflow condition that occurs when the get_contents function processes excessively long lines in NSS files such as /etc/passwd, /etc/group, or /etc/hosts. The function fails to properly validate the length of input data before attempting to process it, leading to heap memory corruption. This heap corruption can manifest in two primary ways: either causing a segmentation fault that results in a denial of service or allowing an attacker to manipulate memory layout to achieve privilege escalation. The vulnerability is particularly dangerous because it operates within the core system libraries that numerous applications depend upon for name resolution and user authentication services.
From an operational perspective, this vulnerability presents significant risk to system security and stability. Local attackers can exploit the heap corruption to either crash critical system services or potentially elevate their privileges to root level access. The impact extends beyond individual system compromise as the NSS functionality affects multiple system components including authentication services, network resolution, and user management systems. The vulnerability's exploitation requires local access but can lead to complete system compromise, making it a serious concern for system administrators. According to CWE classification, this maps to CWE-122: Heap-based Buffer Overflow, which is categorized under the broader weakness of insufficient input validation. The ATT&CK framework would classify this under T1068: Exploitation for Privilege Escalation and T1499: Endpoint Denial of Service.
Mitigation strategies for CVE-2015-5277 primarily involve upgrading to glibc version 2.20 or later, which contains the necessary patches to address the heap corruption issue. System administrators should also implement additional security measures including monitoring for abnormal memory usage patterns and implementing strict input validation for NSS file configurations. The vulnerability demonstrates the critical importance of proper buffer management in system libraries and highlights the need for comprehensive security testing of core components. Organizations should conduct immediate vulnerability assessments to identify systems running affected glibc versions and prioritize patch deployment. Additional defensive measures include restricting local user access where possible and implementing intrusion detection systems to monitor for exploitation attempts. The vulnerability underscores the necessity of maintaining up-to-date system libraries and the potential consequences of failing to apply security patches promptly.