CVE-2026-42618 in NTFS-3G
Summary
by MITRE • 10/07/2026
In NTFS-3G before 2026.7.7, a heap buffer overflow exists in ntfs_decompress() in compress.c that allows an attacker to corrupt one byte of heap memory in the SUID-root ntfs-3g binary by crafting a malicious NTFS image. The overflow is triggered by reading the special crafted 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 library, specifically affecting versions prior to 2026.7.7. This issue manifests as a heap buffer overflow located in the ntfs_decompress function found in compress.c. The root cause of this vulnerability lies in insufficient validation of input data during the decompression process for files stored within an NTFS file system image. When the library processes specially crafted compressed streams, it fails to correctly calculate or enforce bounds on the destination memory buffer allocated for storing the decompressed output. This miscalculation results in writing one byte beyond the end of the allocated heap memory region. While the overflow is limited to a single byte, this precise out-of-bounds write can corrupt adjacent heap metadata or critical data structures managed by the allocator. Such corruption undermines the integrity of the program's internal state and creates an opportunity for arbitrary code execution if the attacker can carefully control the content surrounding the overwritten byte and leverage subsequent memory operations that depend on the corrupted values.
The operational impact is particularly severe because ntfs-3g often runs with elevated privileges, including SUID-root permissions in many Linux distributions to allow non-root users to mount NTFS partitions without requiring root access for every operation. An attacker who can trick a privileged user into opening or reading a maliciously crafted NTFS image file can trigger this heap overflow within the context of the high-privilege ntfs-3g binary. By corrupting one byte of heap memory, an attacker may achieve partial overwrite capabilities that facilitate control over program execution flow. This could lead to remote code execution if the vulnerability is triggered via network-accessible services or local privilege escalation when a user mounts a malicious disk image. The ability to write exactly one byte limits some exploitation techniques but does not preclude successful attacks, especially in conjunction with other memory corruption vulnerabilities or through careful heap grooming strategies that manipulate allocator behavior.
From a classification perspective, this vulnerability aligns with CWE-122, which denotes a heap-based buffer overflow where the data is written beyond the bounds of the allocated heap region. It also relates to CWE-787, concerning out-of-bounds write vulnerabilities in general. In terms of attack vectors and techniques, this flaw supports exploitation paths categorized under MITRE ATT&CK technique T1203, which involves exploiting software for execution by leveraging flaws like buffer overflows. The specific mechanism of triggering the vulnerability through file reading places it within the context of input validation failures that are common in media parsing libraries. Attackers would typically need to construct a malicious NTFS image containing compressed files with malformed headers or data streams designed to trigger the incorrect size calculation during decompression.
Mitigation strategies primarily involve upgrading the ntfs-3g package to version 2026.7.7 or later, where this heap buffer overflow has been patched by implementing proper bounds checking in the ntfs_decompress function. System administrators should ensure that all systems utilizing NTFS file system support have updated libraries installed and are configured for automatic security updates when available. For environments where SUID-root binaries pose a significant risk, additional hardening measures such as restricting mount capabilities to trusted users or using alternative mounting methods with reduced privileges can mitigate the impact of successful exploitation. Furthermore, implementing strict input validation at higher-level application layers that invoke ntfs-3g functions can provide defense-in-depth against malformed inputs derived from untrusted sources like external storage devices or downloaded disk images.