CVE-2015-4265 in Unified Computing System
Summary
by MITRE
Cisco Unified Computing System (UCS) B Blade Server Software 2.2.x before 2.2.6 allows local users to cause a denial of service (host OS or BMC hang) by sending crafted packets over the Inter-IC (I2C) bus, aka Bug ID CSCuq77241.
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Analysis
by VulDB Data Team • 06/20/2022
The vulnerability identified as CVE-2015-4265 affects Cisco Unified Computing System UCS B Blade Server Software versions 2.2.x prior to 2.2.6, representing a critical local privilege escalation and denial of service weakness that impacts the host operating system and Baseboard Management Controller. This flaw exists within the Inter-IC (I2C) bus communication mechanism, which serves as a critical interface for hardware component coordination and system management within the blade server architecture. The vulnerability specifically targets the software stack responsible for processing I2C bus transactions, creating a pathway for malicious local users to exploit the system through carefully crafted packet sequences that can trigger system instability.
The technical implementation of this vulnerability stems from insufficient input validation and error handling within the I2C bus driver components of the UCS B Blade Server software stack. When legitimate I2C packets are malformed or contain unexpected data sequences, the system fails to properly sanitize or reject these inputs, leading to buffer overflows, memory corruption, or state machine failures within the hardware abstraction layer. This issue aligns with CWE-129, which addresses improper validation of length of input buffers, and CWE-125, concerning out-of-bounds read conditions. The vulnerability operates at a low system level where the I2C bus serves as the communication channel between the host processor, BMC, and various hardware components including sensors, power management units, and configuration registers.
From an operational impact perspective, successful exploitation of CVE-2015-4265 can result in complete system unavailability through host OS hang conditions or BMC system lockups, effectively rendering the blade server inoperable until manual intervention occurs. The denial of service can persist for extended periods, potentially causing significant operational disruptions in data center environments where high availability is critical. Network administrators and system operators may experience extended downtime while troubleshooting the affected systems, as the symptoms manifest as system freezes rather than clear error messages, complicating rapid diagnosis and remediation efforts. This vulnerability particularly affects environments where multiple blade servers operate in high-density configurations, as the failure of individual systems can cascade into larger infrastructure issues.
The attack vector requires local access to the affected system, meaning that exploitation typically occurs from within the physical or logical boundary of the target server, though this limitation does not mitigate the severity of the impact. Attackers can leverage this vulnerability through direct system access or by compromising other local services that might provide a foothold within the system. Mitigation strategies include implementing the vendor-provided software patches that address the input validation issues in the I2C bus processing components, along with regular security assessments to identify potential privilege escalation paths. Organizations should also consider network segmentation and access controls to limit local system access, while monitoring for unusual system behavior that might indicate exploitation attempts. The vulnerability demonstrates the importance of robust input validation at all levels of system software, particularly in hardware management interfaces where malformed data can have catastrophic system-wide consequences, aligning with ATT&CK technique T1068 which covers local privilege escalation through system-level vulnerabilities.