CVE-2022-33742 in Xen
Summary
by MITRE • 07/05/2022
Linux disk/nic frontends data leaks T[his CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] Linux Block and Network PV device frontends don't zero memory regions before sharing them with the backend (CVE-2022-26365, CVE-2022-33740). Additionally the granularity of the grant table doesn't allow sharing less than a 4K page, leading to unrelated data residing in the same 4K page as data shared with a backend being accessible by such backend (CVE-2022-33741, CVE-2022-33742).
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Analysis
by VulDB Data Team • 07/19/2022
The vulnerability described in CVE-2022-33742 represents a critical data leakage issue affecting Linux virtualization environments, specifically within disk and network PV (paravirtualized) device frontends. This security flaw manifests in two primary components that together create a significant attack surface for malicious actors seeking to access sensitive information. The root cause lies in the improper memory management practices employed by the Linux kernel's virtualization subsystem, where memory regions are not properly zeroed before being shared with hypervisor backends. This fundamental design oversight creates persistent data leakage channels that can be exploited to access residual information from previous operations or other processes running within the same virtualized environment.
The technical implementation of this vulnerability stems from the lack of proper memory sanitization protocols in the grant table management system used by Xen hypervisor. When virtual machines share memory pages with the hypervisor backend, the system fails to ensure that sensitive data from previous operations remains isolated within the allocated memory regions. The granularity limitation of the grant table system, which operates at 4KB page boundaries, creates additional exposure windows where unrelated data can co-reside within the same memory page as the intended shared data. This architectural constraint means that even when only small amounts of data need to be shared, the entire 4KB page must be allocated, potentially containing remnants of previous operations or data from other virtual machines running on the same host system.
The operational impact of this vulnerability extends beyond simple data leakage to encompass potential information disclosure across multiple virtual environments. Attackers can exploit this weakness to access sensitive data that should remain isolated between different virtual machines or processes, potentially including cryptographic keys, passwords, personal information, or other confidential data. The vulnerability affects both block device and network device frontends, creating widespread exposure across different types of virtualized I/O operations. This issue particularly impacts cloud computing environments and virtualization platforms where multiple tenants share the same physical infrastructure, as the data leakage could enable cross-tenant information disclosure attacks that violate fundamental security isolation principles.
From a cybersecurity perspective, this vulnerability aligns with several common weakness enumerations including CWE-200, which addresses information exposure, and CWE-310, which covers cryptographic weaknesses. The attack patterns associated with this vulnerability map to techniques described in the MITRE ATT&CK framework under T1005, where adversaries access data from local system storage, and T1041, which covers data compression techniques used in exfiltration. The vulnerability represents a classic case of insufficient memory sanitization and improper access control in virtualized environments, creating persistent information leakage channels that can be exploited by both malicious insiders and external attackers with access to the virtualization infrastructure.
Mitigation strategies for this vulnerability require both immediate patching and architectural considerations for long-term security. The primary solution involves updating the Linux kernel to versions containing fixes for the grant table memory management and ensuring proper zeroing of memory regions before sharing with hypervisor backends. Organizations should also implement additional monitoring for unusual memory access patterns and consider implementing memory isolation techniques beyond the standard virtualization boundaries. System administrators should review their virtualization configurations to ensure proper isolation between virtual machines and regularly audit memory usage patterns. The fix addresses the core issue by implementing proper memory sanitization protocols that ensure no residual data remains in memory regions after they are released from use, thereby preventing unauthorized access to previously stored information through the grant table sharing mechanism.