CVE-2026-71220 in Red Hat
Summary
by MITRE • 09/03/2026
A stack out-of-bounds write vulnerability was found in gfs2-utils. In gfs2_edit, the di_height field from on-disk inode metadata is used as an array index without bounds checking, causing a stack buffer overflow that may lead to arbitrary code execution when processing crafted GFS2 filesystem images.
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Analysis
by VulDB Data Team • 09/03/2026
The vulnerability identified in gfs2-utils represents a critical security flaw within the file system editing utility, specifically affecting the gfs2_edit component used for inspecting and modifying GNU File System 2 (GFS2) metadata. This issue stems from improper input validation during the parsing of on-disk inode structures. When an administrator or automated tool processes a GFS2 filesystem image that has been maliciously crafted to contain corrupted metadata, the application fails to verify the integrity of specific fields before using them as control values for memory operations. The primary technical defect lies in how the di_height field is handled; this value, which indicates the height of the inode's indirect block tree structure, is extracted directly from disk without any range checking or bounds verification against known valid limits for GFS2 metadata structures.
From a technical perspective, the absence of boundary checks allows an attacker to supply a di_height value that exceeds the allocated size of internal stack buffers used by gfs2_edit during its traversal and processing routines. Because this unchecked integer is subsequently utilized as an array index or loop counter within functions responsible for handling inode data structures, it triggers a classic stack-based buffer overflow condition. The memory corruption occurs when the application attempts to write data beyond the allocated stack frame boundaries, overwriting adjacent memory locations that may contain return addresses, function pointers, or other critical control flow information. This type of vulnerability is categorized under CWE-121, which defines stack-based buffer overflow as a weakness where software writes data past the end of a stack-allocated buffer due to insufficient bounds checking on input values derived from external sources such as disk files.
The operational impact of this flaw is severe because it potentially allows for arbitrary code execution with the privileges of the user running gfs2_edit. Since file system utilities often require elevated permissions or are run by root during maintenance tasks, successful exploitation could grant an attacker full control over the underlying operating system. An adversary can craft a malicious GFS2 image containing specific inode metadata where the di_height field is set to a large integer value that causes stack corruption in a predictable manner. By carefully controlling the overflowed data, it becomes possible to overwrite return addresses on the stack with shellcode or gadgets from existing libraries, thereby hijacking program execution flow. This aligns with MITRE ATT&CK technique T1203, which covers exploitation for client-side code execution, although in this context, it applies more broadly to local privilege escalation if the utility is run as a privileged user during routine administration tasks involving untrusted or compromised storage media.
Mitigation strategies must address both immediate remediation and long-term defensive coding practices. The most effective solution involves updating gfs2-utils to a patched version where developers have implemented strict validation logic for all metadata fields before they are used in memory allocation or indexing operations. Specifically, the di_height field should be validated against maximum allowable values defined by the GFS2 specification prior to its use as an array index. Additionally, employing compiler-level protections such as stack canaries (stack protector), Address Space Layout Randomization (ASLR), and Data Execution Prevention (DEP) or No-Execute (NX) bits can significantly reduce the likelihood of successful exploitation even if a buffer overflow occurs by making it difficult to predict memory layouts and execute injected code. System administrators should also limit access to gfs2_edit tools, ensuring that only trusted personnel handle potentially unverified filesystem images from external sources, thereby reducing the attack surface for this specific vector.