CVE-2020-25637 in QEMU
Summary
by MITRE • 10/06/2020
A double free memory issue was found to occur in the libvirt API, in versions before 6.8.0, responsible for requesting information about network interfaces of a running QEMU domain. This flaw affects the polkit access control driver. Specifically, clients connecting to the read-write socket with limited ACL permissions could use this flaw to crash the libvirt daemon, resulting in a denial of service, or potentially escalate their privileges on the system. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
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Analysis
by VulDB Data Team • 10/25/2024
The CVE-2020-25637 vulnerability represents a critical double free memory error within the libvirt virtualization management library that impacts versions prior to 680. This flaw exists in the API handling of network interface information requests for running QEMU virtual machines, specifically affecting the polkit access control driver implementation. The vulnerability stems from improper memory management where the same memory block gets freed twice during the processing of network interface queries, creating a condition that can be exploited by authenticated attackers with limited privileges. The issue manifests when clients connect to the read-write socket using restricted access control list permissions, making it particularly dangerous in multi-tenant virtualization environments where privilege separation is crucial.
The technical exploitation of this vulnerability involves leveraging the polkit access control mechanism to send crafted requests that trigger the double free condition in the libvirt daemon's memory management subsystem. When the daemon processes these malformed network interface queries, it attempts to free memory that has already been released, potentially allowing attackers to manipulate memory contents or cause heap corruption. This memory corruption can result in arbitrary code execution or complete daemon crashes, leading to denial of service conditions that disrupt virtualization services. The vulnerability's classification as a CWE-415 double free weakness demonstrates the fundamental flaw in memory management practices within the libvirt codebase, where proper memory deallocation checks are missing or inadequate.
The operational impact of CVE-2020-25637 extends beyond simple service disruption to encompass serious security implications including privilege escalation and data integrity compromise. Attackers with limited ACL permissions can exploit this vulnerability to either crash the libvirt daemon, causing availability issues for virtualized workloads, or potentially escalate their privileges to gain elevated system access. The threat level is particularly concerning for data confidentiality and integrity as the vulnerability could enable attackers to manipulate virtual machine configurations or access sensitive information stored within the virtualization environment. This makes the flaw especially dangerous in enterprise settings where libvirt manages critical infrastructure workloads and where maintaining system availability and data protection is paramount. The vulnerability's potential for privilege escalation directly violates the principle of least privilege and could allow attackers to move laterally within virtualized environments.
Mitigation strategies for CVE-2020-25637 primarily focus on immediate version upgrades to libvirt 680 or later, which contain the necessary patches to prevent the double free condition. Organizations should also implement network segmentation and access controls to limit exposure of the libvirt daemon's read-write socket to trusted clients only. Additionally, monitoring systems should be configured to detect unusual patterns in network interface query requests that might indicate exploitation attempts. The implementation of proper input validation and memory management practices within the polkit driver components should be reviewed to prevent similar issues. Security teams should also consider implementing privilege separation mechanisms and regular security audits of virtualization management interfaces to identify potential weaknesses in access control implementations. This vulnerability highlights the importance of maintaining up-to-date virtualization infrastructure and proper security hardening practices in cloud and enterprise environments.