CVE-2023-38430 in Linux
Summary
by MITRE • 07/18/2023
An issue was discovered in the Linux kernel before 6.3.9. ksmbd does not validate the SMB request protocol ID, leading to an out-of-bounds read.
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Analysis
by VulDB Data Team • 08/09/2023
The vulnerability identified as CVE-2023-38430 resides within the Linux kernel's ksmbd implementation, which serves as a server-side SMB/CIFS protocol handler enabling file and printer sharing capabilities. This flaw affects kernel versions prior to 6.3.9 and represents a critical validation failure that undermines the security of network file sharing services. The issue manifests when ksmbd processes incoming SMB requests without properly verifying the protocol identifier field, creating a pathway for malicious actors to exploit the system through crafted network traffic. The vulnerability specifically impacts the SMB protocol handling mechanism where the kernel fails to validate the protocol ID field in incoming requests, allowing unauthorized access to memory locations beyond the intended buffer boundaries.
The technical exploitation of this vulnerability stems from an out-of-bounds read condition that occurs when ksmbd processes SMB requests containing malformed protocol identifiers. This type of flaw falls under CWE-129, which describes improper validation of the length of input data, and more specifically aligns with CWE-125, representing out-of-bounds read conditions. The protocol ID validation failure creates a scenario where an attacker can send specially crafted SMB packets that cause the kernel to access memory locations beyond the allocated buffer space. This memory access violation can result in information disclosure, system instability, or potentially enable further exploitation depending on the memory layout and available data. The vulnerability operates at the kernel level, making it particularly dangerous as it can be leveraged to gain unauthorized access to sensitive kernel memory regions.
From an operational perspective, this vulnerability presents significant risk to organizations relying on Linux-based SMB file servers, particularly those running older kernel versions. The impact extends beyond simple information disclosure as the out-of-bounds read could potentially reveal kernel memory contents including sensitive data, credentials, or system configuration details. Network-based attacks exploiting this vulnerability require minimal privileges and can be executed remotely, making them particularly attractive to threat actors. The vulnerability affects systems where ksmbd is enabled and actively processing SMB requests, potentially compromising entire file sharing infrastructures. Organizations using Linux distributions with kernel versions earlier than 6.3.9 are at risk, with the exploitation potentially leading to system crashes, data leakage, or privilege escalation depending on the specific memory access patterns. The vulnerability's presence in the kernel's SMB handling code means that any service relying on ksmbd for file sharing is potentially exposed.
Mitigation strategies for CVE-2023-38430 primarily focus on immediate kernel version upgrades to 6.3.9 or later, which contain the necessary patches addressing the protocol ID validation issue. System administrators should prioritize updating their kernel versions and ensure all related services are restarted to apply the security fixes. Additionally, network-level mitigations can be implemented through firewall rules that restrict SMB traffic to trusted networks, although this approach only reduces exposure rather than eliminating the vulnerability. The patch addresses the root cause by implementing proper validation of the SMB protocol ID field before processing incoming requests, preventing the out-of-bounds read condition. Organizations should also consider implementing monitoring solutions to detect anomalous SMB traffic patterns that might indicate exploitation attempts. Security teams should perform comprehensive vulnerability assessments to identify all systems running affected kernel versions and ensure proper patch management procedures are in place to prevent similar issues in the future. The remediation process should include thorough testing of updated kernel versions to ensure compatibility with existing SMB services and applications.