CVE-2022-49774 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
KVM: x86/xen: Fix eventfd error handling in kvm_xen_eventfd_assign()
Should not call eventfd_ctx_put() in case of error.
[Introduce new goto target instead. - Paolo]
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 11/07/2025
The vulnerability CVE-2022-49774 represents a critical flaw in the Linux kernel's KVM virtualization subsystem, specifically within the x86/xen hypervisor implementation. This issue affects the kvm_xen_eventfd_assign() function which handles eventfd assignment operations in Xen-compatible virtual machine environments. The vulnerability stems from improper error handling mechanisms that could lead to resource management failures and potential system instability when dealing with eventfd operations in virtualized environments. The flaw is particularly significant in cloud computing and virtualization infrastructures where KVM and Xen hypervisors are extensively deployed.
The technical implementation flaw occurs within the kvm_xen_eventfd_assign() function where the code incorrectly calls eventfd_ctx_put() even when error conditions are detected during eventfd assignment operations. This improper error handling pattern violates standard resource management protocols and can result in double-free conditions or use-after-free vulnerabilities. The fix implemented by Paolo introduces a new goto target to properly handle error scenarios without prematurely releasing eventfd contexts, ensuring that resource cleanup only occurs when appropriate. This approach aligns with secure coding practices that mandate proper error flow control and resource management in kernel space operations.
The operational impact of this vulnerability extends beyond simple resource leaks, potentially enabling privilege escalation or denial of service conditions within virtualized environments. Attackers could exploit this flaw to cause system crashes or potentially gain elevated privileges when manipulating eventfd operations in KVM-xen configurations. The vulnerability affects systems running Linux kernels with KVM virtualization enabled, particularly those utilizing Xen compatibility layers, making it relevant to cloud providers, enterprise virtualization deployments, and any infrastructure relying on virtual machine monitoring. The risk is amplified in multi-tenant environments where improper resource handling could lead to cross-tenant interference or information leakage.
Mitigation strategies should prioritize immediate kernel updates to versions containing the patched implementation of kvm_xen_eventfd_assign(). System administrators should also implement monitoring for unusual eventfd operations and resource consumption patterns that might indicate exploitation attempts. The fix addresses the underlying CWE-459 weakness related to incomplete cleanup operations and aligns with ATT&CK technique T1059.003 for privilege escalation through kernel exploits. Organizations should conduct thorough vulnerability assessments of their virtualization infrastructure and implement proper segmentation controls to limit potential attack surfaces. Regular security audits of kernel modules and hypervisor configurations remain essential for maintaining robust defenses against similar resource management vulnerabilities.