CVE-2017-6949 in CHICKEN Scheme
Summary
by MITRE
An issue was discovered in CHICKEN Scheme through 4.12.0. When using a nonstandard CHICKEN-specific extension to allocate an SRFI-4 vector in unmanaged memory, the vector size would be used in unsanitised form as an argument to malloc(). With an unexpected size, the impact may have been a segfault or buffer overflow.
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Analysis
by VulDB Data Team • 08/25/2024
The vulnerability CVE-2017-6949 represents a critical memory safety issue within the CHICKEN Scheme implementation that affects versions through 4.12.0. This flaw resides in the handling of SRFI-4 vector allocation mechanisms, specifically when utilizing CHICKEN-specific extensions for unmanaged memory operations. The vulnerability stems from insufficient input validation and sanitization processes that occur during memory allocation procedures, creating a pathway for potentially exploitable memory corruption conditions.
The technical flaw manifests when CHICKEN Scheme processes SRFI-4 vector allocation requests through its nonstandard extension mechanisms designed for unmanaged memory operations. During this process, the system accepts vector size parameters directly from user input without proper sanitization or validation checks before passing these values to the underlying malloc() function. This direct parameter transmission creates a classic buffer overflow vulnerability pattern where maliciously crafted size values can cause memory allocation failures, leading to segmentation faults or more severe buffer overflow conditions that could potentially be exploited for arbitrary code execution.
The operational impact of this vulnerability extends beyond simple program crashes, as it creates a potential attack surface for privilege escalation and system compromise. When an attacker can manipulate the vector size parameters to exceed reasonable memory allocation limits, the system may experience segmentation faults that could be leveraged to cause denial of service conditions or potentially enable more sophisticated exploitation techniques. The vulnerability particularly affects applications that heavily utilize CHICKEN Scheme's memory management features and SRFI-4 vector operations, making it a significant concern for systems relying on this implementation.
This vulnerability aligns with CWE-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-bounds Write) categories, representing a clear violation of secure coding practices regarding input validation and memory management. From an ATT&CK framework perspective, this issue could be categorized under T1059 (Command and Scripting Interpreter) and T1068 (Exploitation for Privilege Escalation) as it represents a foundational memory corruption vulnerability that could enable further attack vectors. The vulnerability demonstrates a fundamental failure in the principle of least privilege and input sanitization, where user-provided parameters are not adequately validated before being used in critical system operations.
Mitigation strategies should focus on implementing comprehensive input validation for all memory allocation parameters, including bounds checking and size validation before any malloc() operations occur. System administrators should immediately upgrade to CHICKEN Scheme versions that have patched this vulnerability, as the fix typically involves adding proper sanitization routines to validate vector size parameters. Additionally, deployment of runtime protections such as address space layout randomization and stack canaries can provide additional defense-in-depth measures. The vulnerability also underscores the importance of following secure coding guidelines and implementing proper memory management practices, particularly when dealing with low-level memory allocation functions that are susceptible to manipulation through crafted input parameters.