CVE-2026-64217 in Linux
Summary
by MITRE • 07/24/2026
In the Linux kernel, the following vulnerability has been resolved:
netfs: Fix overrun check in netfs_extract_user_iter()
Fix netfs_extract_user_iter() so that if iov_iter_extract_pages() overfills pages[], then those pages don't get included in the iterator constructed at
the end of the function. If there was an overfill, memory corruption has already happened.
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Analysis
by VulDB Data Team • 07/24/2026
The vulnerability identified in the Linux kernel's netfs subsystem represents a critical memory safety issue within the netfs_extract_user_iter() function that could lead to arbitrary code execution or system instability. This flaw resides in the network filesystem handling code where user space data is processed through iov_iter_extract_pages() function, which is responsible for extracting page structures from user memory regions. The vulnerability stems from inadequate bounds checking during the page extraction process, creating a scenario where buffer overflows can occur when the extraction routine fills more pages than allocated in the pages[] array.
The technical flaw manifests when iov_iter_extract_pages() overfills the pages[] array beyond its intended capacity, causing subsequent operations to reference memory locations outside the allocated buffer boundaries. This overrun condition occurs during the construction of the final iterator object where the function attempts to incorporate potentially corrupted page references into the resulting data structure. The vulnerability is particularly dangerous because it operates at the kernel level where memory corruption can immediately translate into privilege escalation opportunities or complete system compromise. According to CWE-121, this represents a stack-based buffer overflow condition that can be exploited through improper bounds checking in memory management operations.
The operational impact of this vulnerability extends beyond simple memory corruption as it affects the core networking functionality of Linux systems that utilize network filesystems. Systems relying on NFS, CIFS, or other network storage protocols are at risk when processing user data through the affected code path. The memory corruption can manifest in various ways including kernel panics, data loss, or more insidiously, provide attackers with opportunities to execute malicious code with kernel privileges. Attackers could potentially exploit this vulnerability by crafting specific network filesystem requests that trigger the overrun condition, particularly when dealing with large data transfers or malformed input from untrusted network sources.
Mitigation strategies for this vulnerability should focus on immediate patch application as provided by the Linux kernel security team, which corrects the bounds checking logic in netfs_extract_user_iter() to prevent inclusion of overfilled pages in the final iterator construction. System administrators should prioritize deployment of updated kernel versions across all affected systems and monitor for potential exploitation attempts through network intrusion detection systems. Additional protective measures include implementing proper input validation for network filesystem operations, restricting access to sensitive network storage resources, and maintaining regular security audits of kernel components that handle user data transfers. The fix aligns with ATT&CK technique T1068 by preventing privilege escalation through kernel memory corruption vulnerabilities, while also addressing CWE-787 which covers out-of-bounds writes in kernel space operations. Organizations should also consider implementing kernel module signing and trusted boot processes to further reduce the attack surface for such low-level memory corruption exploits.