CVE-2024-50074 in Linux
Summary
by MITRE • 10/29/2024
In the Linux kernel, the following vulnerability has been resolved:
parport: Proper fix for array out-of-bounds access
The recent fix for array out-of-bounds accesses replaced sprintf() calls blindly with snprintf(). However, since snprintf() returns the would-be-printed size, not the actually output size, the length calculation can still go over the given limit.
Use scnprintf() instead of snprintf(), which returns the actually output letters, for addressing the potential out-of-bounds access properly.
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Analysis
by VulDB Data Team • 08/21/2025
The vulnerability CVE-2024-50074 addresses a critical array out-of-bounds access issue within the Linux kernel's parallel port subsystem. This flaw specifically affects the parport driver component responsible for managing parallel port communications and device interactions. The vulnerability stems from an improper implementation of buffer size calculations when handling string formatting operations within kernel space. The initial mitigation attempt involved replacing sprintf() calls with snprintf() to prevent buffer overflows, but this approach introduced a new vulnerability due to a fundamental misunderstanding of how these functions behave in kernel contexts. The core issue manifests when the kernel attempts to format and output string data to buffers, where the calculation of output length becomes problematic due to the differing return values between snprintf() and the actual output produced. This vulnerability represents a classic example of improper input validation and buffer management in kernel code, where developers must account for the precise behavior of string manipulation functions in privileged execution contexts.
The technical flaw in this vulnerability lies in the incorrect assumption about the return value semantics of snprintf() versus scnprintf() functions within kernel space operations. When snprintf() is used, it returns the number of characters that would have been written to the buffer had it been large enough, rather than the actual number of characters written. This distinction becomes critical in kernel contexts where buffer boundaries must be strictly enforced to prevent memory corruption. The parport subsystem's implementation incorrectly relied on snprintf() to determine safe buffer limits, leading to potential out-of-bounds memory access when the calculated output size exceeded the allocated buffer capacity. The vulnerability specifically impacts the kernel's parallel port handling code where formatted output operations occur during device status reporting and error logging. This issue falls under CWE-129, which describes improper validation of array index bounds, and more specifically aligns with CWE-787, representing out-of-bounds write operations. The flaw demonstrates poor understanding of kernel security principles where buffer overflow protections must account for the exact memory layout and access patterns in kernel space.
The operational impact of CVE-2024-50074 extends beyond simple data corruption, potentially enabling privilege escalation or system instability in environments utilizing parallel port devices. Attackers could exploit this vulnerability by manipulating parallel port device interactions to cause buffer overflows that might lead to kernel memory corruption, resulting in system crashes, denial of service conditions, or potentially arbitrary code execution with kernel privileges. The vulnerability affects systems running Linux kernels with parallel port support, particularly those using legacy hardware interfaces or specialized industrial equipment that relies on parport functionality. Since this is a kernel-level vulnerability, the impact is severe and affects all processes running on the affected system, as kernel memory corruption can lead to complete system compromise. The vulnerability is particularly concerning in embedded systems, industrial control environments, or any scenario where parallel port devices are actively used, as these systems may not receive regular security updates or may have limited mitigation capabilities. The exploitability of this vulnerability is moderate to high, as it requires only legitimate access to parallel port devices or their associated drivers to trigger the problematic code path.
The recommended mitigation for CVE-2024-50074 involves applying the official kernel patch that replaces snprintf() with scnprintf() throughout the affected parport subsystem code. This change ensures that the actual output length is correctly calculated and validated against buffer boundaries, preventing the out-of-bounds access condition. System administrators should prioritize updating their kernel versions to include the patched code, particularly in production environments where parallel port devices are active. The fix specifically addresses the root cause by utilizing scnprintf() which returns the actual number of characters written to the buffer, thereby providing accurate length calculations for buffer boundary validation. Organizations should also consider implementing monitoring for unusual parallel port activity or device access patterns that might indicate exploitation attempts. The mitigation aligns with ATT&CK technique T1068, which covers local privilege escalation through kernel vulnerabilities, and T1566, covering initial access via physical or network-based attacks. Regular kernel security audits should include verification of similar patterns throughout the kernel codebase, as this vulnerability demonstrates how seemingly simple string handling operations can introduce critical security flaws when not properly understood in kernel contexts. The patch implementation should be tested thoroughly in development environments before deployment to production systems to ensure compatibility with existing parallel port device configurations and drivers.