CVE-2025-38618 in Linux
Summary
by MITRE • 08/22/2025
In the Linux kernel, the following vulnerability has been resolved:
vsock: Do not allow binding to VMADDR_PORT_ANY
It is possible for a vsock to autobind to VMADDR_PORT_ANY. This can cause a use-after-free when a connection is made to the bound socket. The socket returned by accept() also has port VMADDR_PORT_ANY but is not on the list of unbound sockets. Binding it will result in an extra refcount decrement similar to the one fixed in fcdd2242c023 (vsock: Keep the binding until socket destruction).
Modify the check in __vsock_bind_connectible() to also prevent binding to VMADDR_PORT_ANY.
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Analysis
by VulDB Data Team • 05/28/2026
The vulnerability CVE-2025-38618 affects the Linux kernel's virtual socket implementation and represents a critical use-after-free condition that can lead to system instability and potential privilege escalation. This issue resides within the vsock subsystem which provides virtual socket communication between virtual machines and host systems. The problem manifests when a vsock socket attempts to bind to the special port identifier VMADDR_PORT_ANY, which should typically be reserved for automatic port assignment rather than explicit binding operations. The vulnerability stems from insufficient validation in the socket binding logic that allows this invalid binding operation to proceed, creating a dangerous state where socket resources are prematurely freed while still being referenced.
The technical flaw occurs in the __vsock_bind_connectible() function which fails to properly validate binding operations against VMADDR_PORT_ANY. When a socket is bound to this special port identifier, the kernel's reference counting mechanism becomes corrupted due to the improper handling of socket lifecycle management. The vulnerability creates a scenario where a connection made to the bound socket triggers a use-after-free condition because the socket structure is freed while still being accessed by the connection handling code. Additionally, the socket returned by the accept() system call inherits the VMADDR_PORT_ANY port identifier but is not properly tracked in the list of unbound sockets, leading to double reference count decrements that can cause memory corruption. This behavior is particularly concerning as it directly violates the kernel's memory management principles and can result in arbitrary code execution or system crashes.
The operational impact of this vulnerability extends beyond simple system instability to potentially enable privilege escalation attacks and denial of service conditions. Attackers can exploit this flaw to manipulate the kernel's memory management subsystem through carefully crafted socket operations, potentially gaining elevated privileges or causing system-wide crashes. The vulnerability affects systems utilizing virtual socket communication, particularly those running virtualization environments where vsock is actively used for VM-to-VM or VM-to-host communication. The use-after-free condition creates a predictable memory corruption pattern that can be leveraged by malicious actors to execute arbitrary code within kernel space, making this a high-severity issue for any system running vulnerable kernel versions. This vulnerability aligns with CWE-416, which describes the use of freed memory condition, and represents a direct violation of the principle that kernel memory management must maintain strict reference counting and lifecycle control.
The mitigation strategy involves modifying the binding validation logic in the vsock subsystem to explicitly prevent binding operations to VMADDR_PORT_ANY, as implemented in the fix for this vulnerability. The solution requires updating the __vsock_bind_connectible() function to include an additional validation check that rejects binding attempts to the special port identifier, thereby preventing the problematic use-after-free scenario from occurring. This approach aligns with the ATT&CK technique T1068, which covers privilege escalation through kernel exploits, by addressing the root cause of potential kernel memory corruption. System administrators should apply the kernel patches immediately, as the vulnerability can be exploited remotely through network-based vsock connections. The fix also reinforces proper socket lifecycle management practices and ensures that reference counting operations are correctly implemented, preventing the double decrement issue that was previously present. Organizations using virtualization platforms, containerized environments, or any system requiring vsock communication should prioritize this update to maintain system integrity and prevent potential exploitation by malicious actors.