CVE-2014-0143 in QEMU
Summary
by MITRE
Multiple integer overflows in the block drivers in QEMU, possibly before 2.0.0, allow local users to cause a denial of service (crash) via a crafted catalog size in (1) the parallels_open function in block/parallels.c or (2) bochs_open function in bochs.c, a large L1 table in the (3) qcow2_snapshot_load_tmp in qcow2-snapshot.c or (4) qcow2_grow_l1_table function in qcow2-cluster.c, (5) a large request in the bdrv_check_byte_request function in block.c and other block drivers, (6) crafted cluster indexes in the get_refcount function in qcow2-refcount.c, or (7) a large number of blocks in the cloop_open function in cloop.c, which trigger buffer overflows, memory corruption, large memory allocations and out-of-bounds read and writes.
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Analysis
by VulDB Data Team • 06/16/2021
The vulnerability identified as CVE-2014-0143 represents a critical class of integer overflow flaws affecting QEMU's block drivers, specifically targeting versions prior to 2.0.0. This vulnerability exploits fundamental arithmetic operations that fail to properly validate input parameters, creating opportunities for attackers to manipulate memory allocation and buffer boundaries through crafted input data. The issue spans multiple functions across different block driver implementations, indicating a systemic weakness in input validation and integer handling throughout QEMU's storage subsystem. These vulnerabilities are particularly dangerous because they can be triggered by local users who have access to the system, making them exploitable in scenarios where untrusted input is processed through virtualized storage mechanisms.
The technical exploitation occurs through several distinct code paths that all share the common pattern of integer overflows leading to memory corruption. In the parallels_open function within block/parallels.c, attackers can craft a malicious catalog size that causes integer overflow during memory allocation calculations. Similarly, the bochs_open function in bochs.c demonstrates the same vulnerability pattern with large L1 table sizes that trigger overflow conditions. The qcow2_snapshot_load_tmp function in qcow2-snapshot.c and qcow2_grow_l1_table function in qcow2-cluster.c both exhibit integer overflows when processing large L1 table operations. The bdrv_check_byte_request function in block.c shows how request size validation can be bypassed through crafted requests, while the get_refcount function in qcow2-refcount.c demonstrates issues with cluster index handling. Finally, the cloop_open function in cloop.c contains similar vulnerabilities with large block counts. These patterns align with CWE-190, which specifically addresses integer overflow conditions, and demonstrate how improper input validation can lead to buffer overflows and memory corruption.
The operational impact of these vulnerabilities extends beyond simple denial of service scenarios, as they can potentially enable more sophisticated attacks through memory corruption. When integer overflows occur, they typically result in unexpected memory allocations that can trigger buffer overflows, leading to memory corruption that may allow attackers to execute arbitrary code or cause system crashes. The memory allocation issues stemming from these overflows can also consume excessive system resources, potentially leading to resource exhaustion attacks. These vulnerabilities are particularly concerning in virtualized environments where QEMU serves as a critical component for storage handling, as they can be exploited to compromise the integrity of virtual machine storage operations. The fact that these issues affect multiple block drivers suggests that the underlying problem lies in fundamental design patterns rather than isolated implementation errors, making the vulnerability more widespread and difficult to remediate.
Mitigation strategies for CVE-2014-0143 should focus on comprehensive input validation and integer overflow protection throughout QEMU's block driver implementations. The most effective immediate solution involves upgrading to QEMU version 2.0.0 or later, where these vulnerabilities have been addressed through proper integer overflow checks and input validation. Organizations should implement robust input sanitization routines that verify all size parameters before memory allocation operations, particularly in functions that handle disk image metadata and storage requests. The implementation of bounds checking mechanisms in memory allocation routines can prevent the exploitation of integer overflows by ensuring that calculated buffer sizes remain within safe limits. Additionally, defensive programming practices such as using safe integer arithmetic libraries and implementing comprehensive testing procedures for boundary conditions should be adopted. These mitigations align with ATT&CK technique T1059.007 for command and scripting interpreter, as they address potential exploitation vectors through proper input handling and memory management. The vulnerability serves as a critical reminder of the importance of proper integer overflow protection in systems handling untrusted input data, particularly in virtualization platforms where such issues can have cascading effects on system stability and security.