CVE-2026-42617 in ntfs-3g
Summary
by MITRE • 10/07/2026
In NTFS-3G before 2026.7.7, a heap buffer overflow exists in ntfs_ir_to_ib() in index.c that allows an attacker to corrupt heap memory in the SUID-root ntfs-3g binary by crafting a malicious NTFS image. The overflow is triggered by extending a directory, e.g., by creating a file.
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Analysis
by VulDB Data Team • 10/07/2026
The vulnerability identified as CVE-2026-XXXX represents a critical security flaw within the NTFS-3G open-source driver, specifically affecting versions prior to 2026.7.7. This issue manifests as a heap buffer overflow located in the ntfs_ir_to_ib function found within the index.c source file. The root cause of this vulnerability lies in insufficient boundary checks when processing directory structures during NTFS volume operations. When an attacker crafts a malicious NTFS image containing specially formatted directory entries, they can exploit this logic error to write data beyond the allocated bounds of a heap buffer. This type of memory corruption is classified under CWE-122, which denotes a heap-based buffer overflow where input validation fails to restrict the size of data written to dynamically allocated memory regions.
The operational impact of this vulnerability is severe due to the typical execution context of the ntfs-3g binary. In many Linux and Unix-like environments, users mount NTFS partitions using root privileges or with elevated permissions to ensure proper access control and file system integrity. Because the vulnerable function operates within a SUID-root binary, any successful exploitation allows an attacker to achieve arbitrary code execution with root-level privileges on the host system. The trigger mechanism involves extending a directory structure, such as by creating a new file within a maliciously crafted NTFS volume. As the driver processes these extended directories, it invokes ntfs_ir_to_ib without adequately verifying that the target buffer has sufficient space for the incoming data structures derived from the malformed image.
From an offensive security perspective, this vulnerability aligns with ATT&CK technique T1059, specifically command and script interpretation via system utilities or libraries like NTFS-3G. An attacker can leverage this heap overflow to overwrite adjacent memory structures on the heap, potentially manipulating function pointers or return addresses stored in nearby objects. This manipulation facilitates control flow hijacking, allowing the execution of shellcode injected into the process memory space. The ability to corrupt heap memory in a privileged binary effectively bypasses standard user-level isolation mechanisms, granting full administrative access to the compromised system.
Mitigation strategies primarily involve updating the NTFS-3G installation to version 2026.7.7 or later, where this boundary check has been corrected by the developers. For environments that cannot immediately patch the software, operational mitigations include restricting the use of SUID-root binaries for mounting untrusted media and implementing strict file system access controls. Additionally, deploying intrusion detection systems capable of monitoring heap corruption anomalies may provide early warning indicators of exploitation attempts. Security administrators should also audit scripts or automated processes that mount NTFS volumes from external sources to ensure they are not inadvertently triggering this vulnerability through routine directory operations.