CVE-2026-46569: 
CBL Mariner Análisis y mitigación de vulnerabilidades

CVE-2026-46569 is a heap buffer overflow vulnerability in ntfs-3g, the read/write NTFS driver for FUSE. 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 Ubuntu 22.04 LTS, 24.04 LTS, and 26.04 LTS, as well as Debian Linux. The CVE was inserted into Feedly's threat intelligence on July 15, 2026, with Ubuntu's security advisory (USN-8554-1) published on July 16, 2026. The estimated CVSS severity is Medium (Ubuntu Advisory, OSV).

The root cause is a heap buffer overflow (CWE-122) in ntfs-3g's index block processing logic, specifically when the tail data of an index block is copied into a newly allocated memory buffer during NTFS image parsing. An attacker can trigger this by supplying a specially crafted or corrupt NTFS filesystem image for mounting or processing. The precondition for exploitation is local access — the attacker must be able to cause the system to process a malicious NTFS image, such as by mounting a crafted disk image. This vulnerability is part of a broader set of heap buffer overflow issues disclosed simultaneously in ntfs-3g (CVE-2026-42617, CVE-2026-42618, CVE-2026-46570, CVE-2026-46572, CVE-2026-56135) (Ubuntu Advisory, oss-sec).

Successful exploitation could allow a local attacker to execute arbitrary code in the context of the ntfs-3g process, which may run with elevated privileges depending on system configuration. This could lead to privilege escalation, unauthorized access to sensitive data, or full system compromise. The vulnerability's impact is limited to systems that process attacker-controlled NTFS images, reducing the attack surface to local or physically proximate threat actors (Ubuntu Advisory).

No public proof-of-concept exploit code or in-the-wild exploitation has been reported for CVE-2026-46569 at this time. The CVE status remains "Reserved" with limited public technical detail beyond the vendor advisory. Exploitation requires local access to supply a crafted NTFS image, which limits the practical attack surface. The vulnerability has been detected by Nessus plugins (IDs 327190, 329286, 329281), indicating scanner coverage is available (Tenable, Tenable). No EPSS score or CISA KEV catalog entry has been identified for this CVE.

1. Prepare a malicious NTFS image: Craft a corrupt or specially structured NTFS filesystem image that contains a malformed index block designed to trigger the heap buffer overflow during tail-data copying.
2. Deliver the image to the target: Place the crafted NTFS image on a medium accessible to the target system (e.g., USB drive, network share, or downloadable file).
3. Trigger ntfs-3g processing: Cause the target system to mount or process the malicious NTFS image using ntfs-3g (e.g., via ntfs-3g /dev/sdX /mnt/point or by inserting a crafted USB drive on a system with automount enabled).
4. Trigger the overflow: During index block processing, ntfs-3g copies tail data into a freshly allocated heap buffer without adequate bounds checking, causing a heap buffer overflow.
5. Achieve code execution: With a carefully crafted payload, the overflow can overwrite heap metadata or function pointers to redirect execution flow and execute arbitrary code with the privileges of the ntfs-3g process (Ubuntu Advisory, oss-sec).

• Process: Unexpected crashes or segmentation faults in the ntfs-3g process, particularly when mounting external or removable NTFS volumes.
• Logs: System logs (/var/log/syslog, dmesg) showing ntfs-3g process crashes, heap corruption errors, or abnormal termination signals (SIGSEGV, SIGABRT) when processing NTFS images.
• File System: Unexpected files written to mount points or temporary directories by the ntfs-3g process; presence of unknown NTFS image files in user-accessible directories.
• Network: Outbound connections from the ntfs-3g process or its parent (unusual for a filesystem driver) may indicate post-exploitation activity.

Ubuntu has released patched package versions addressing CVE-2026-46569 as part of USN-8554-1. Users should update to the following versions: 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; Ubuntu 22.04 LTS — ntfs-3g 1:2021.8.22-3ubuntu1.4. SUSE has also released a security update (SUSE-SU-2026:3213-1). A standard system update (apt upgrade or equivalent) is the recommended remediation. As a workaround, administrators can disable automounting of external NTFS volumes and restrict which users can invoke ntfs-3g to reduce exposure (Ubuntu Advisory, SUSE Advisory).

The vulnerability was disclosed via the oss-security mailing list and prompted prompt responses from major Linux distributions including Ubuntu, Debian, and SUSE, all releasing security advisories within days of disclosure. Linux security news aggregators such as LinuxSecurity.com and LinuxCompatible.org covered the Ubuntu advisory. The Solus Linux community also noted the fix in their weekly update digest (oss-sec, LinuxSecurity, Solus).