CVE-2025-22038 in Linux
Summary
by MITRE • 04/16/2025
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: validate zero num_subauth before sub_auth is accessed
Access psid->sub_auth[psid->num_subauth - 1] without checking
if num_subauth is non-zero leads to an out-of-bounds read. This patch adds a validation step to ensure num_subauth != 0 before sub_auth is accessed.
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Analysis
by VulDB Data Team • 02/15/2026
The vulnerability identified as CVE-2025-22038 resides within the Linux kernel's ksmbd subsystem, which provides SMB/CIFS file sharing capabilities for Linux systems. This flaw represents a critical out-of-bounds memory access issue that could potentially be exploited to disrupt system operations or gain unauthorized access to sensitive data. The ksmbd component serves as a server implementation for the Server Message Block protocol, commonly used for file sharing in enterprise environments and Windows networked systems.
The technical root cause of this vulnerability stems from inadequate input validation within the SMB protocol handling code. Specifically, the flaw occurs when processing security identifiers (SIDs) during authentication processes. The code attempts to access the array element psid->sub_auth[psid->num_subauth - 1] without first verifying that psid->num_subauth is greater than zero. This condition creates a scenario where the system performs a memory read operation at an address that may be outside the allocated bounds of the sub_auth array, leading to undefined behavior and potential information disclosure.
The operational impact of this vulnerability extends beyond simple denial of service scenarios. An attacker who can manipulate SMB authentication requests could potentially trigger the out-of-bounds read condition, which may result in memory corruption that could be leveraged for privilege escalation or information disclosure attacks. The vulnerability affects systems running Linux kernels with ksmbd support, particularly those configured to provide SMB file sharing services to clients. This makes it especially concerning for enterprise environments where SMB services are actively used for file sharing and collaboration.
This vulnerability aligns with CWE-129, which describes improper validation of array indices, and represents a classic example of an out-of-bounds read condition that can lead to memory corruption. From an adversarial perspective, this flaw could be categorized under the ATT&CK technique T1078.002, which involves valid accounts used for lateral movement, as an attacker might exploit this condition to gain additional privileges or access to system resources. The patch implemented addresses the issue by introducing a validation check that ensures num_subauth is non-zero before any access to the sub_auth array occurs, thereby preventing the out-of-bounds memory access.
Security professionals should prioritize patching systems running affected kernel versions, particularly those with active SMB services enabled. Organizations should also implement monitoring for unusual SMB authentication patterns that might indicate exploitation attempts. The fix demonstrates proper defensive programming practices by implementing input validation before array access operations, aligning with established security principles that emphasize the importance of bounds checking in memory management operations. Regular security audits of kernel subsystems and protocol implementations should be conducted to identify similar validation gaps that could potentially lead to more severe vulnerabilities in the future.