CVE-2023-32256 in Linux
Summary
by MITRE • 08/01/2025
A flaw was found in the Linux kernel's ksmbd component. A race condition between smb2 close operation and logoff in multichannel connections could result in a use-after-free issue.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 08/05/2025
The vulnerability identified as CVE-2023-32256 resides within the Linux kernel's ksmbd component, which serves as an SMB/CIFS server implementation designed to provide file sharing capabilities over network protocols. This flaw manifests as a race condition that occurs during the interaction between smb2 close operations and logoff procedures within multichannel SMB connections. The ksmbd subsystem operates under the broader context of Linux kernel security mechanisms that manage network file sharing services, making it a critical component for enterprise environments relying on SMB protocol implementations.
The technical nature of this vulnerability stems from improper synchronization mechanisms within the kernel's SMB implementation where concurrent operations can lead to memory management inconsistencies. Specifically, when multiple channels are established in an SMB connection and simultaneous close operations occur alongside logoff requests, the race condition allows for a scenario where memory allocated to connection resources may be freed while still being referenced by other concurrent processes. This use-after-free condition represents a classic memory safety vulnerability that can potentially be exploited to execute arbitrary code or cause system instability.
The operational impact of this vulnerability extends beyond simple system crashes or denial of service conditions. Attackers could leverage this race condition to gain unauthorized access to system resources, potentially escalating privileges or disrupting critical network services. The multichannel nature of SMB connections makes this particularly concerning as it affects environments where high-performance network file sharing is essential, such as enterprise data centers, storage servers, and collaborative work environments. The vulnerability affects systems running Linux kernels with ksmbd support, making it relevant to organizations maintaining SMB server implementations in their infrastructure.
Mitigation strategies for CVE-2023-32256 should prioritize immediate kernel updates from vendors that address the race condition through proper synchronization mechanisms. System administrators must implement comprehensive patch management protocols to ensure all affected systems receive the necessary security updates. Additional defensive measures include monitoring network traffic for unusual SMB activity patterns and implementing network segmentation to limit potential attack surfaces. Organizations should also consider disabling unnecessary SMB server functionality when not required, as this reduces the attack surface for exploitation attempts. The vulnerability aligns with CWE-367, which addresses time-of-check to time-of-use race conditions, and could potentially map to ATT&CK technique T1059 for execution through kernel-level code injection. Regular security assessments of network services and kernel configurations remain essential for maintaining robust security postures against similar memory safety vulnerabilities.