CVE-2026-42618: 
CBL Mariner Análisis y mitigación de vulnerabilidades

CVE-2026-42618 is a heap buffer overflow vulnerability in ntfs-3g, the FUSE-based NTFS read/write driver. It occurs when copying the tail data of an index block to a freshly allocated block while processing a corrupt or maliciously crafted NTFS filesystem image. The vulnerability affects ntfs-3g packages across multiple Linux distributions including Ubuntu 22.04 LTS, 24.04 LTS, and 26.04 LTS, as well as Debian and SUSE. It was publicly disclosed in July 2026 and carries an estimated CVSS severity of Medium (Ubuntu Advisory, OSS-Sec).

The root cause is a heap buffer overflow (CWE-122) in ntfs-3g's index block processing logic, specifically when the tail portion of an index block is copied into a newly allocated buffer without adequate bounds checking. An attacker can trigger this by supplying a corrupt or specially crafted NTFS filesystem image to a system that mounts or processes it via ntfs-3g. The vulnerability is part of a broader set of heap buffer overflow and out-of-bounds read issues discovered in ntfs-3g around the same time (CVE-2026-42616, CVE-2026-42617, CVE-2026-46569, CVE-2026-46570, CVE-2026-46572, CVE-2026-56135) (Ubuntu Advisory, OSS-Sec).

Successful exploitation allows a local attacker to potentially execute arbitrary code in the context of the ntfs-3g process, which may run with elevated privileges depending on system configuration. The primary impact is on integrity and availability, with a risk of privilege escalation if ntfs-3g is invoked with elevated permissions (e.g., via SUID or sudo). Confidentiality impact is limited compared to the related out-of-bounds read CVEs in the same advisory (Ubuntu Advisory).

No public proof-of-concept exploit code or in-the-wild exploitation has been reported for CVE-2026-42618 as of the time of this report. The CVE status remains "Reserved" in the NVD, indicating full details have not yet been formally published. Exploitation requires local access to a system where a malicious or corrupt NTFS image can be processed by ntfs-3g. The vulnerability has been detected by Nessus plugins (IDs 327152, 327201, 327650, 329286) and is not currently listed in the CISA KEV catalog (Tenable, OSV).

1. Prepare a malicious NTFS image: Craft a corrupt NTFS filesystem image with a malformed index block whose tail data, when copied to a freshly allocated buffer, triggers a heap buffer overflow in ntfs-3g's index processing code.
2. Deliver the image to the target: Place the crafted NTFS image on a medium or path accessible to the target system (e.g., a USB drive, network share, or local file).
3. Trigger ntfs-3g processing: Cause the target system to mount or process the malicious image using ntfs-3g — this may occur automatically (e.g., via automount on removable media insertion) or manually via ntfs-3g /dev/sdX /mnt/point.
4. Achieve code execution: The heap buffer overflow corrupts heap metadata or adjacent allocations, potentially allowing control of program execution flow and arbitrary code execution in the ntfs-3g process context (Ubuntu Advisory, OSS-Sec).

• Logs: System logs (/var/log/syslog, dmesg) showing ntfs-3g crashes, segmentation faults, or heap corruption errors when mounting NTFS volumes.
• Process: Unexpected child processes spawned from ntfs-3g or unusual process termination signals (SIGSEGV, SIGABRT) associated with ntfs-3g.
• File System: Presence of unusual or externally supplied NTFS image files in temporary directories or removable media mount points.
• Network: Unexpected outbound connections from the system shortly after an NTFS volume is mounted, which could indicate post-exploitation activity.

Ubuntu has released patched package versions addressing CVE-2026-42618 and related vulnerabilities: Ubuntu 26.04 LTS (ntfs-3g 1:2022.10.3-5ubuntu1.1), Ubuntu 24.04 LTS (ntfs-3g 1:2022.10.3-1.2ubuntu3.2), and Ubuntu 22.04 LTS (ntfs-3g 1:2021.8.22-3ubuntu1.4). SUSE has also released a security update (SUSE-SU-2026:3213-1 / 3214-1). Debian has issued a corresponding update tracked via OSV. Users should apply the standard system update for their distribution. As a workaround, restricting the ability of unprivileged users to mount NTFS volumes or disabling automounting of removable media reduces exposure (Ubuntu Advisory, SUSE Advisory).

The vulnerability was disclosed via the OSS-Security mailing list in July 2026 alongside several related ntfs-3g heap overflow issues. Linux distribution vendors including Ubuntu, Debian, and SUSE responded promptly with security advisories and patched packages within days of disclosure. Coverage was noted on Linux security news aggregators and community forums (OSS-Sec, Linux Security).