CVE-2022-50856 in Linux
Summary
by MITRE • 12/30/2025
In the Linux kernel, the following vulnerability has been resolved:
cifs: Fix xid leak in cifs_ses_add_channel()
Before return, should free the xid, otherwise, the xid will be leaked.
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Analysis
by VulDB Data Team • 06/07/2026
The vulnerability identified as CVE-2022-50856 represents a memory management flaw within the Linux kernel's CIFS (Common Internet File System) implementation that specifically affects the cifs_ses_add_channel() function. This issue manifests as a resource leak where the XID (eXtended Identifier) is not properly released when the function exits, leading to a gradual consumption of system resources over time. The CIFS protocol implementation in the Linux kernel handles network file sharing operations between Linux systems and Windows-based file servers, making this vulnerability particularly significant in enterprise environments where file sharing services are heavily utilized.
The technical root cause of this vulnerability stems from improper resource cleanup within the cifs_ses_add_channel() function, which is responsible for adding additional channels to existing CIFS sessions. When this function processes a channel addition request, it allocates an XID for tracking the operation but fails to execute the necessary cleanup routine before returning control to the calling process. This XID leak occurs because the function does not invoke the appropriate deallocation mechanism that would normally free the XID resource, leaving it in a state where it remains allocated in memory even though the operation has completed. The XID serves as a unique identifier for network operations within the CIFS protocol and is essential for maintaining proper session state tracking and transaction management.
The operational impact of this vulnerability extends beyond simple memory consumption, as it can lead to system instability and performance degradation in environments with high CIFS usage patterns. Over time, repeated calls to cifs_ses_add_channel() will accumulate XID leaks, potentially exhausting available resources and causing system slowdowns or even service interruptions. This resource exhaustion can be particularly problematic in server environments where multiple concurrent CIFS connections are maintained, as the cumulative effect of these leaks can rapidly deplete system memory resources. The vulnerability is especially concerning in high-availability environments where continuous file sharing operations are critical for business operations, as it can contribute to unexpected system failures and require unplanned maintenance windows for resource recovery.
Mitigation strategies for CVE-2022-50856 should focus on applying the official kernel patches that correct the resource management issue within the cifs_ses_add_channel() function. System administrators should prioritize updating their Linux kernel versions to include the fix that ensures proper XID deallocation before function return. The vulnerability aligns with CWE-404, which addresses improper resource release or unmanaged resources, and represents a classic example of resource leak vulnerabilities that can be exploited to cause denial of service conditions. From an ATT&CK framework perspective, this vulnerability could be leveraged by adversaries to perform resource exhaustion attacks against systems running affected kernel versions, potentially leading to system instability or service disruption. Organizations should also implement monitoring solutions to detect unusual memory consumption patterns that might indicate the presence of this vulnerability, particularly in environments with extensive CIFS usage. Regular kernel updates and security patch management procedures should be enforced to prevent exploitation of this and similar resource management vulnerabilities in the Linux kernel's network file sharing implementations.