CVE-2018-1635 in Informix Dynamic Server Enterprise Edition
Summary
by MITRE
Stack-based buffer overflow in oninit in IBM Informix Dynamic Server Enterprise Edition 12.1 allows an authenticated user to execute predefined code with root privileges, such as escalating to a root shell. IBM X-Force ID: 144439.
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Analysis
by VulDB Data Team • 11/27/2023
The vulnerability identified as CVE-2018-1635 represents a critical stack-based buffer overflow flaw within the oninit component of IBM Informix Dynamic Server Enterprise Edition version 12.1. This issue specifically affects the initialization process of the database server and creates a pathway for authenticated attackers to achieve arbitrary code execution with elevated privileges. The vulnerability resides in how the oninit utility handles input parameters during the server startup sequence, creating an exploitable condition that can be leveraged by malicious actors who have already established authentication credentials to the system. The flaw demonstrates a classic stack buffer overflow where insufficient bounds checking allows an attacker to overwrite adjacent memory locations, potentially leading to complete system compromise. This vulnerability is particularly dangerous because it operates at the system initialization level, meaning it can be exploited during the critical startup phase when the database server is most vulnerable and when the system is running with elevated privileges.
The technical implementation of this buffer overflow stems from improper input validation within the oninit utility's parameter processing routines. When the utility receives command-line arguments or configuration parameters during startup, it fails to properly validate the length of input data before copying it to fixed-size stack buffers. This allows an attacker to provide input that exceeds the allocated buffer space, causing a stack overwrite that can be carefully crafted to redirect program execution flow. The vulnerability is classified under CWE-121 Stack-based Buffer Overflow, which specifically addresses buffer overflows occurring in stack memory regions. The attack vector requires an authenticated user account with sufficient privileges to execute the oninit utility, but the successful exploitation results in privilege escalation to root level, making the impact significantly more severe than typical local privilege escalation vulnerabilities.
The operational impact of CVE-2018-1635 extends beyond simple code execution as it provides a complete path to system compromise through privilege escalation. An attacker who successfully exploits this vulnerability can gain root shell access, which provides unrestricted control over the entire database server and underlying operating system. This level of access enables the attacker to modify or delete critical system files, install backdoors, exfiltrate sensitive data, and establish persistent access to the compromised environment. The vulnerability is particularly concerning in enterprise environments where database servers often contain sensitive corporate data and where root access could lead to lateral movement throughout the network infrastructure. The exploitation process typically involves crafting malicious input parameters that trigger the buffer overflow condition, followed by carefully constructed payload delivery that leverages the stack overwrite to execute arbitrary code at the highest privilege level. This vulnerability aligns with ATT&CK technique T1068, which covers the use of local privilege escalation techniques to gain system-level access.
Mitigation strategies for CVE-2018-1635 require immediate implementation of vendor-provided patches and updates to address the root cause of the buffer overflow vulnerability. IBM has released security fixes for this issue in subsequent versions of the Informix Dynamic Server, and organizations should prioritize upgrading to patched releases to eliminate the risk. Additionally, implementing strict input validation measures and limiting the execution privileges of the oninit utility can help reduce the attack surface. Network segmentation and access controls should be enforced to limit the number of authenticated users who can potentially exploit this vulnerability. Security monitoring should include detection of unusual oninit utility executions and parameter patterns that could indicate exploitation attempts. System administrators should also implement principle of least privilege practices, ensuring that only authorized personnel have access to the database server initialization processes. Regular security assessments and vulnerability scanning should be conducted to identify similar buffer overflow conditions in other system components, as this class of vulnerability remains prevalent in enterprise software environments. The vulnerability serves as a reminder of the critical importance of proper input validation and memory management practices in preventing exploitation of buffer overflow conditions.