CVE-2023-38432 in Linux
Summary
by MITRE • 07/18/2023
An issue was discovered in the Linux kernel before 6.3.10. fs/smb/server/smb2misc.c in ksmbd does not validate the relationship between the command payload size and the RFC1002 length specification, leading to an out-of-bounds read.
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Analysis
by VulDB Data Team • 08/12/2025
The vulnerability identified as CVE-2023-38432 represents a critical out-of-bounds read flaw within the Linux kernel's ksmbd implementation that affects versions prior to 6.3.10. This issue resides in the file system subsystem specifically within the SMB2 protocol handling code located at fs/smb/server/smb2misc.c. The flaw manifests when the ksmbd server component fails to properly validate the relationship between command payload size and the RFC1002 length specification that governs SMB network packet formatting. This validation gap creates a scenario where maliciously crafted SMB2 requests can trigger memory access violations that extend beyond the intended buffer boundaries.
The technical nature of this vulnerability stems from insufficient input validation mechanisms within the SMB2 protocol parser. When processing incoming SMB2 commands, the ksmbd implementation relies on the RFC1002 length field to determine the expected payload size, but fails to cross-verify this value against the actual command payload being processed. This discrepancy allows attackers to craft packets where the reported length in the RFC1002 header does not match the actual data present in the command payload, creating a condition where the kernel's memory access routines attempt to read beyond allocated buffer boundaries. Such out-of-bounds reads can lead to information disclosure, system instability, or potentially arbitrary code execution depending on the memory layout and subsequent processing of the corrupted data.
The operational impact of this vulnerability extends beyond simple memory corruption as it affects the core SMB2 server functionality that many enterprise systems rely upon for file sharing and network access. Systems running affected kernel versions with ksmbd enabled are particularly vulnerable since the flaw exists in the protocol handling layer that processes network requests from remote clients. Attackers could exploit this vulnerability to gain unauthorized access to sensitive information stored in kernel memory, potentially leading to credential theft, privilege escalation, or complete system compromise. The vulnerability's presence in the kernel's file system subsystem means that any service relying on SMB2 file sharing protocols could become a potential attack vector, affecting everything from file servers to network-attached storage systems.
Mitigation strategies for CVE-2023-38432 primarily focus on immediate kernel version upgrades to 6.3.10 or later where the vulnerability has been patched. Organizations should prioritize patching systems running affected kernel versions, particularly those with ksmbd services enabled and exposed to untrusted networks. Network segmentation and access controls should be implemented to limit exposure of vulnerable systems to potential attackers. The vulnerability aligns with CWE-129, which addresses improper validation of length fields, and demonstrates characteristics consistent with ATT&CK technique T1071.004 for application layer protocol manipulation. System administrators should also consider implementing network monitoring to detect anomalous SMB2 traffic patterns that might indicate exploitation attempts, while maintaining regular vulnerability assessments to identify other potential protocol handling flaws within the kernel's network stack implementations.