CVE-2025-38737 in Linux
Summary
by MITRE • 09/05/2025
In the Linux kernel, the following vulnerability has been resolved:
cifs: Fix oops due to uninitialised variable
Fix smb3_init_transform_rq() to initialise buffer to NULL before calling netfs_alloc_folioq_buffer() as netfs assumes it can append to the buffer it is given. Setting it to NULL means it should start a fresh buffer, but the value is currently undefined.
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Analysis
by VulDB Data Team • 02/09/2026
The vulnerability identified as CVE-2025-38737 represents a critical uninitialized variable flaw within the Linux kernel's CIFS (Common Internet File System) implementation that could lead to system instability and potential denial of service conditions. This issue specifically affects the smb3_init_transform_rq() function which handles the initialization of transform request operations in SMB3 protocol implementations. The flaw occurs when the buffer variable is not properly initialized before being passed to the netfs_alloc_folioq_buffer() function, creating a scenario where undefined memory contents are interpreted as valid buffer references. This uninitialized state can cause unpredictable behavior during kernel memory management operations and represents a classic example of improper initialization patterns that have been classified under CWE-457 as use of uninitialized variable.
The technical execution of this vulnerability stems from the assumption that netfs_alloc_folioq_buffer() can append data to an existing buffer structure, but the calling function fails to initialize the buffer pointer to NULL before this operation. When the buffer remains uninitialized, it may contain arbitrary data from previous memory operations, causing the netfs subsystem to attempt operations on invalid memory references or corrupted buffer structures. This creates a potential for kernel oops conditions where the system encounters a page fault or memory access violation, leading to kernel panic or system crash. The vulnerability is particularly concerning because it operates at kernel level where such failures can result in complete system instability and compromise the integrity of the entire operating environment. From an operational perspective, this flaw aligns with ATT&CK technique T1499.004 which involves network disruption through system resource exhaustion or kernel-level corruption.
The impact of this vulnerability extends beyond simple system crashes to potentially enable more sophisticated attack vectors if exploited in conjunction with other kernel flaws. An attacker could potentially leverage this uninitialized variable to manipulate memory layout or cause heap corruption, though direct exploitation for privilege escalation appears less likely given the nature of the flaw. The vulnerability affects systems running Linux kernels with CIFS/SMB3 support, particularly those implementing network file sharing services or systems accessing remote SMB3 shares. Organizations utilizing extensive network file sharing infrastructure or those with multiple SMB3 connections would be most at risk from this vulnerability. The fix implemented addresses the root cause by explicitly initializing the buffer variable to NULL before invoking the netfs allocation function, ensuring that the subsystem receives a clean starting point for buffer management operations.
Mitigation strategies for CVE-2025-38737 primarily focus on immediate kernel updates and patches provided by Linux kernel maintainers and distribution vendors. System administrators should prioritize applying the relevant security patches to all affected systems, particularly those hosting critical network services or serving as file servers. Additionally, monitoring for kernel oops messages or system instability patterns that may indicate exploitation attempts should be implemented. Network segmentation and access controls can provide additional defense in depth by limiting exposure of systems to potentially malicious SMB3 connections. The vulnerability demonstrates the importance of proper variable initialization in kernel code and highlights the need for comprehensive code review processes that include static analysis tools capable of detecting uninitialized variable usage patterns. Organizations should also consider implementing automated patch management systems to ensure rapid deployment of security fixes across their infrastructure, as kernel-level vulnerabilities like this one can have far-reaching consequences for system availability and security posture.