CISA Alerts to Active Exploits of Linux Kernel Ownership Flaw

The Cybersecurity and Infrastructure Security Agency (CISA) issued an urgent alert regarding active exploitation of a critical Linux kernel vulnerability, tracked as CVE-2023-0386, which has now been added to the Known Exploited Vulnerabilities (KEV) Catalog.

This flaw, rooted in the OverlayFS subsystem of the Linux kernel, allows local users to escalate privileges and potentially gain root-level access on affected systems—a scenario that poses significant risks to both enterprise and cloud environments.

Linux Kernel Improper Ownership Management Vulnerability – CVE-2023-0386

CVE-2023-0386 is classified as an improper ownership management vulnerability (CWE-282) within the OverlayFS subsystem of the Linux kernel.

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The flaw emerges when a user copies a file with special capabilities from a nosuid mount into another mount, due to the kernel’s failure to properly clear setuid and setgid bits during the copy-up operation.

This oversight enables unauthorized users to execute files with elevated privileges, effectively allowing a non-privileged user to escalate to root access.

A proof-of-concept exploit has demonstrated that attackers can weaponize this bug in seconds, particularly in environments where unprivileged users have access to file operations or can mount overlays—common scenarios in containerized, virtualized, or multi-user Linux deployments.

The vulnerability affects a broad range of Linux distributions and kernel versions, especially those running OverlayFS and supporting user namespaces.

Systems at risk include enterprise servers, cloud virtual machines, containers, and even some Windows environments leveraging the Windows Subsystem for Linux (WSL). 

The flaw is especially dangerous in shared hosting or multi-tenant environments, where privilege escalation could compromise entire systems.

CISA’s alert highlights that exploitation efforts have accelerated following public disclosure and the availability of proof-of-concept code.

Attackers are leveraging automated tools to scan for and exploit unpatched systems, with real-world campaigns already observed targeting both exposed Linux servers and containerized workloads.

Mitigation and Guidance

CISA has mandated all Federal Civilian Executive Branch (FCEB) agencies to remediate CVE-2023-0386 by July 8, 2025. Recommended actions include:

• Apply vendor patches and mitigations as soon as possible.
• Follow BOD 22-01 guidance for cloud services and vulnerability management.
• Discontinue use of vulnerable products if no mitigation is available.

Organizations of all sizes are strongly urged to treat the KEV Catalog as a critical resource and to prioritize remediation of this vulnerability, given its active exploitation and potential for severe impact.

CISA’s addition of CVE-2023-0386 to the KEV Catalog underscores the ongoing threat posed by vulnerabilities in foundational open-source components.

Immediate action is required to patch affected systems and mitigate the risk of compromise from this actively exploited Linux kernel flaw.

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