CVE-2010-0826 in libnss-db
Summary
by MITRE
The Free Software Foundation (FSF) Berkeley DB NSS module (aka libnss-db) 2.2.3pre1 reads the DB_CONFIG file in the current working directory, which allows local users to obtain sensitive information via a symlink attack involving a setgid or setuid application that uses this module.
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Analysis
by VulDB Data Team • 05/05/2026
The vulnerability identified as CVE-2010-0826 resides within the Free Software Foundation Berkeley DB NSS module, specifically version 2.2.3pre1, which represents a critical security flaw in the Name Service Switch functionality of Unix-like operating systems. This module serves as a bridge between the system's name resolution mechanisms and Berkeley Database files, enabling applications to query user and group information from database-backed sources rather than traditional flat files. The core issue manifests when applications that utilize this NSS module execute with elevated privileges through setuid or setgid permissions, creating a dangerous attack surface where malicious users can exploit the module's behavior to access sensitive system information.
The technical flaw stems from the module's improper handling of the DB_CONFIG file, which is typically used to configure Berkeley Database parameters. Under normal circumstances, this configuration file should be located in a secure, predictable location within the system's database directory structure. However, the vulnerable implementation causes the module to indiscriminately read DB_CONFIG files from the current working directory of the executing process, rather than enforcing proper access controls or path validation. This behavior becomes exploitable when a setuid or setgid application executes in a directory controlled by an unprivileged user, allowing that user to place a malicious symlink or file named DB_CONFIG in the working directory. When the privileged application subsequently loads the NSS module, it inadvertently reads the attacker-controlled configuration file, potentially exposing sensitive database connection parameters, authentication credentials, or other confidential information that would normally be restricted to privileged access.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates a persistent attack vector that can be leveraged by local users to escalate privileges or gather intelligence for further exploitation. The vulnerability is particularly dangerous because it operates silently in the background, with no explicit error messages or warnings, making it difficult to detect through standard monitoring mechanisms. According to CWE classification, this represents a weakness categorized under CWE-22 - Improper Limitation of a Pathname to a Restricted Directory, which specifically addresses the risk of path traversal and file access issues. The vulnerability aligns with ATT&CK technique T1068 - Exploitation for Privilege Escalation, as it enables local users to exploit setuid/setgid applications to gain elevated system privileges. Additionally, the issue falls under T1552 - Unsecured Credentials, where the exposure of database configuration information could lead to further compromise of database systems and their associated sensitive data.
Mitigation strategies for this vulnerability require a multi-layered approach focusing on both immediate remediation and long-term system hardening. The most effective immediate solution involves upgrading to a patched version of the libnss-db module where the vulnerable behavior has been corrected to properly validate file paths and prevent reading configuration files from arbitrary locations. System administrators should also implement proper file system permissions and directory access controls, ensuring that directories containing setuid/setgid applications are not writable by unprivileged users. The principle of least privilege should be enforced by reviewing and minimizing the use of setuid/setgid applications where possible, as these permissions inherently increase the attack surface. Additionally, implementing mandatory access controls through mechanisms such as SELinux or AppArmor can provide additional layers of protection by restricting the module's ability to access files outside of designated directories. Security monitoring should include detection of suspicious symlink creation patterns in directories where privileged applications execute, as this behavior often indicates an attempted exploitation of this vulnerability. The vulnerability also underscores the importance of proper input validation and secure coding practices, particularly in modules that handle sensitive system information and operate in privileged contexts.