CVE-2025-71265 in Linux
Summary
by MITRE • 03/18/2026
In the Linux kernel, the following vulnerability has been resolved:
fs: ntfs3: fix infinite loop in attr_load_runs_range on inconsistent metadata
We found an infinite loop bug in the ntfs3 file system that can lead to a Denial-of-Service (DoS) condition.
A malformed NTFS image can cause an infinite loop when an attribute header indicates an empty run list, while directory entries reference it as containing actual data. In NTFS, setting evcn=-1 with svcn=0 is a valid way to represent an empty run list, and run_unpack() correctly handles this by checking if evcn + 1 equals svcn and returning early without parsing any run data. However, this creates a problem when there is metadata inconsistency, where the attribute header claims to be empty (evcn=-1) but the caller expects to read actual data. When run_unpack() immediately returns success upon seeing this condition, it leaves the runs_tree uninitialized with run->runs as a NULL. The calling function attr_load_runs_range() assumes that a successful return means that the runs were loaded and sets clen to 0, expecting the next run_lookup_entry() call to succeed. Because runs_tree remains uninitialized, run_lookup_entry() continues to fail, and the loop increments vcn by zero (vcn += 0), leading to an infinite loop.
This patch adds a retry counter to detect when run_lookup_entry() fails consecutively after attr_load_runs_vcn(). If the run is still not found on the second attempt, it indicates corrupted metadata and returns -EINVAL, preventing the Denial-of-Service (DoS) vulnerability.
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Analysis
by VulDB Data Team • 05/20/2026
The vulnerability identified as CVE-2025-71265 represents a critical denial-of-service condition within the Linux kernel's ntfs3 file system implementation. This flaw manifests as an infinite loop that occurs when processing malformed NTFS images containing inconsistent metadata. The issue specifically affects the interaction between the attribute loading mechanism and run list parsing functions within the ntfs3 driver. The vulnerability exploits a fundamental inconsistency between metadata headers and actual data structures, creating a scenario where the file system parser becomes trapped in an endless loop without proper termination conditions.
The technical root cause stems from the ntfs3 driver's handling of empty run lists in NTFS metadata structures. When an attribute header indicates an empty run list through the specific combination of evcn=-1 and svcn=0, the run_unpack() function correctly identifies this condition and returns early without processing run data. However, this optimization creates a problematic edge case when metadata inconsistency occurs, where the attribute header claims to be empty while directory entries reference actual data content. The function run_unpack() returns successfully upon detecting the empty run list condition, leaving the runs_tree data structure uninitialized with run->runs set to NULL. This incomplete initialization creates a cascading failure where subsequent functions cannot properly handle the uninitialized state, leading to the core infinite loop mechanism.
The operational impact of this vulnerability extends beyond simple system stability concerns to potentially disrupt critical file system operations across affected Linux systems. When an attacker or malicious actor presents a specially crafted NTFS image containing the inconsistent metadata pattern, the kernel's ntfs3 driver will enter an infinite loop during attribute processing, consuming CPU resources and preventing legitimate file system operations from completing. This condition effectively creates a denial-of-service scenario that can impact system availability, particularly in environments where NTFS file systems are actively mounted or accessed. The vulnerability is particularly concerning as it can be triggered through normal file system access patterns without requiring privileged operations, making it exploitable in various operational contexts.
The mitigation strategy implemented in this patch introduces a retry counter mechanism to detect and terminate the infinite loop condition before it can cause system instability. This approach specifically targets the sequence where run_lookup_entry() fails consecutively after attr_load_runs_vcn() operations, identifying when the system encounters corrupted metadata that cannot be properly resolved through normal processing paths. The patch implements a detection mechanism that recognizes when the same run lookup operation fails multiple times in succession, indicating that the metadata inconsistency cannot be resolved through normal parsing procedures. Upon detecting this condition, the system returns -EINVAL error code instead of continuing the infinite loop, thereby preventing the denial-of-service scenario while maintaining system stability.
This vulnerability aligns with CWE-835, which describes the weakness of infinite loops in software systems, and demonstrates how improper handling of edge cases in file system metadata processing can lead to system-wide availability issues. The attack pattern follows typical denial-of-service methodologies documented in the MITRE ATT&CK framework under the T1499 category for network denial-of-service, where system resources are consumed to prevent normal operations. The patch implementation represents a defensive programming approach that includes proper error detection and graceful degradation when encountering corrupted data structures, ensuring that the file system can recover from metadata inconsistencies rather than becoming trapped in processing loops.