CVE-2025-52890 in incus
Summary
by MITRE • 06/25/2025
Incus is a system container and virtual machine manager. When using an ACL on a device connected to a bridge, Incus versions 6.12 and 6.13generates nftables rules that partially bypass security options `security.mac_filtering`, `security.ipv4_filtering` and `security.ipv6_filtering`. This can lead to ARP spoofing on the bridge and to fully spoof another VM/container on the same bridge. Commit 254dfd2483ab8de39b47c2258b7f1cf0759231c8 contains a patch for the issue.
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Analysis
by VulDB Data Team • 06/25/2025
CVE-2025-52890 represents a critical security vulnerability in Incus container and virtual machine manager affecting versions 6.12 and 6.13. This flaw resides in the nftables rule generation process when Access Control Lists are applied to devices connected to bridges within the virtualized environment. The vulnerability specifically targets the security filtering mechanisms that are designed to protect network communications between virtual machines and containers. When ACLs are configured on bridge-connected devices, the system generates nftables rules that fail to properly enforce the security.mac_filtering, security.ipv4_filtering, and security.ipv6_filtering options. This partial bypass of security controls creates a significant attack surface that allows malicious actors to exploit the network isolation properties of the virtualized environment.
The technical implementation of this vulnerability stems from how Incus processes and translates ACL configurations into nftables rule sets. When a device is connected to a bridge and ACLs are applied, the system should enforce strict network filtering policies that prevent unauthorized communication between virtual machines and containers. However, the flawed implementation in versions 6.12 and 6.13 generates nftables rules that do not fully respect the security options, creating gaps in the network protection layer. This design flaw specifically impacts the MAC address filtering, IPv4 packet filtering, and IPv6 packet filtering capabilities that are fundamental to maintaining network isolation in containerized environments. The vulnerability manifests as a failure to properly enforce network boundaries that should prevent communication between different virtual entities sharing the same bridge infrastructure.
The operational impact of this vulnerability extends beyond simple network isolation breaches and creates conditions ripe for active exploitation. An attacker who gains access to a virtual machine or container within the same bridge network can leverage this vulnerability to perform ARP spoofing attacks against other VMs or containers on the same bridge. This capability allows for man-in-the-middle attacks where the malicious entity can intercept, modify, or redirect network traffic between legitimate virtual machines and containers. The vulnerability essentially undermines the fundamental security principle of network segmentation that is essential for maintaining the integrity and confidentiality of virtualized environments. The potential for lateral movement within a virtualized infrastructure becomes significantly elevated, as attackers can use this technique to compromise multiple systems sharing the same network bridge.
From a cybersecurity perspective, this vulnerability aligns with several ATT&CK framework techniques including T1046 Network Service Scanning, T1566 Phishing, and T1071.004 Application Layer Protocol DNS, as it enables network reconnaissance and lateral movement capabilities. The vulnerability also corresponds to CWE-284 Improper Access Control, CWE-310 Cryptographic Issues, and CWE-276 Incorrect Default Permissions, highlighting the multi-faceted nature of the security breach. Organizations utilizing Incus for container and virtual machine management face substantial risk from this vulnerability, particularly in environments where multiple tenants share the same infrastructure or where network isolation is critical for compliance requirements. The impact is especially severe in cloud environments, data centers, and multi-tenant deployments where maintaining strict network boundaries is essential for security posture.
The patch referenced in commit 254dfd2483ab8de39b47c2258b7f1cf0759231c8 addresses the core issue by ensuring that nftables rules properly enforce all security filtering options when ACLs are applied to bridge-connected devices. This fix corrects the rule generation process to maintain the intended security boundaries and prevents the partial bypass of MAC, IPv4, and IPv6 filtering mechanisms. Organizations should immediately update their Incus installations to versions that include this patch to eliminate the risk of ARP spoofing attacks and unauthorized network communication between virtual machines and containers. The mitigation strategy should also include network monitoring to detect potential exploitation attempts and regular security audits of virtualized environments to ensure proper network isolation is maintained. Additionally, administrators should review and validate their existing ACL configurations to ensure they do not inadvertently create similar security gaps in their virtualized infrastructure deployments.