CVE-2015-8521 in Tivoli Storage Manager Fastback
Summary
by MITRE
Buffer overflow in the server in IBM Tivoli Storage Manager FastBack 5.5.x and 6.x before 6.1.12.2 allows remote attackers to execute arbitrary code via a crafted command, a different vulnerability than CVE-2015-8519, CVE-2015-8520, and CVE-2015-8522.
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Analysis
by VulDB Data Team • 02/03/2019
The vulnerability identified as CVE-2015-8521 represents a critical buffer overflow flaw within the server component of IBM Tivoli Storage Manager FastBack software versions 5.5.x and 6.x prior to 6.1.12.2. This security weakness specifically targets the command processing functionality of the FastBack server, creating a potential pathway for remote code execution that could be exploited by malicious actors without requiring authentication credentials. The vulnerability operates at the application layer where the server fails to properly validate input lengths when processing crafted commands, leading to memory corruption that can be leveraged to gain unauthorized system access. The flaw is categorized under CWE-121 as a stack-based buffer overflow, which occurs when data is written beyond the boundaries of a fixed-length buffer allocated on the stack. This particular vulnerability demonstrates the classic characteristics of a remote code execution vector where an attacker can craft malicious input to overwrite adjacent memory locations, potentially allowing for arbitrary code execution with the privileges of the affected service account.
The technical exploitation of CVE-2015-8521 requires an attacker to send a specially crafted command to the vulnerable FastBack server service, which then processes this input without adequate bounds checking. When the server receives the malformed command, it attempts to store the data in a buffer that is insufficiently sized to accommodate the input, resulting in a buffer overflow condition that can be manipulated to redirect program execution flow. The attack surface is particularly concerning as it enables remote exploitation over network connections, eliminating the need for physical access or local system compromise. This vulnerability is distinct from related issues CVE-2015-8519, CVE-2015-8520, and CVE-2015-8522, each representing separate code paths that could lead to similar outcomes but through different implementation flaws in the software architecture. The attack methodology aligns with ATT&CK technique T1203 which involves the use of malicious command and control channels, though in this case the vulnerability itself provides the initial access vector rather than a post-exploitation technique.
The operational impact of this vulnerability extends beyond simple system compromise to potentially affect data integrity and availability within storage environments managed by IBM Tivoli Storage Manager FastBack. Organizations utilizing affected versions face significant risk of unauthorized data access, modification, or deletion, particularly in environments where backup and recovery operations are critical for business continuity. The vulnerability affects both the 5.5.x and 6.x release lines, indicating a widespread exposure across multiple generations of the software, which complicates remediation efforts for organizations with mixed version deployments. The remote nature of the exploit means that attackers can target these systems from anywhere on the network, potentially from outside the organization's perimeter, making network segmentation and access controls less effective as protective measures. Security professionals should consider this vulnerability in the context of broader threat landscape analysis, as it represents a potential entry point for more sophisticated attacks that could leverage the compromised system as a staging area for lateral movement within network environments. The vulnerability's classification as a remote code execution flaw places it in a high-risk category that requires immediate attention and remediation to prevent potential data breaches or system compromise.
Organizations should implement immediate mitigations including applying the vendor-provided security patches for IBM Tivoli Storage Manager FastBack versions 6.1.12.2 and later, which address the buffer overflow condition through proper input validation and boundary checking mechanisms. Network-based mitigations should include firewall rules that restrict access to FastBack server ports to trusted sources only, while also implementing intrusion detection systems to monitor for suspicious command patterns that might indicate exploitation attempts. The remediation process should involve thorough testing of patches in non-production environments before deployment to ensure compatibility with existing backup and recovery workflows. Additionally, organizations should conduct comprehensive vulnerability assessments to identify any other systems running affected versions of FastBack or similar software components that might be exposed to similar vulnerabilities. Regular security monitoring and log analysis should be enhanced to detect anomalous command execution patterns that could indicate exploitation attempts, while maintaining updated threat intelligence feeds to understand the evolving tactics used by adversaries targeting storage management systems. The vulnerability highlights the importance of maintaining up-to-date security patches across all enterprise software components, particularly those managing critical data infrastructure and backup operations.