CVE-2026-23265 in Linux
Summary
by MITRE • 03/18/2026
In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix to do sanity check on node footer in {read,write}_end_io
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kernel BUG at fs/f2fs/data.c:358! Call Trace: <IRQ> blk_update_request+0x5eb/0xe70 block/blk-mq.c:987 blk_mq_end_request+0x3e/0x70 block/blk-mq.c:1149 blk_complete_reqs block/blk-mq.c:1224 [inline]
blk_done_softirq+0x107/0x160 block/blk-mq.c:1229 handle_softirqs+0x283/0x870 kernel/softirq.c:579 __do_softirq kernel/softirq.c:613 [inline]
invoke_softirq kernel/softirq.c:453 [inline]
__irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1050 </IRQ>
In f2fs_write_end_io(), it detects there is inconsistency in between node page index (nid) and footer.nid of node page.
If footer of node page is corrupted in fuzzed image, then we load corrupted node page w/ async method, e.g. f2fs_ra_node_pages() or f2fs_ra_node_page(), in where we won't do sanity check on node footer, once node page becomes dirty, we will encounter this bug after node page writeback.
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Analysis
by VulDB Data Team • 06/01/2026
The vulnerability CVE-2026-23265 represents a critical flaw in the Linux kernel's F2FS (Flash-Friendly File System) implementation that arises from inadequate node footer validation during asynchronous I/O operations. This issue manifests as a kernel BUG triggered at fs/f2fs/data.c:358, indicating a fundamental failure in the system's ability to maintain data integrity when processing node pages. The vulnerability specifically impacts the read_end_io and write_end_io functions where the system performs sanity checks on node footers, but these checks are bypassed during asynchronous node page loading operations. The flaw stems from the inconsistent handling of node page indices between the node page index (nid) and the footer.nid field, creating a scenario where corrupted node page footers can be loaded without proper validation.
The technical execution of this vulnerability occurs through the asynchronous node page loading mechanisms such as f2fs_ra_node_pages() and f2fs_ra_node_page() functions, which operate without performing the necessary sanity checks on node footers. When a fuzzed image contains corrupted node page footers, these corrupted pages are loaded asynchronously and remain in a dirty state. The issue becomes apparent only during subsequent writeback operations when the system attempts to validate the node page consistency, leading to the kernel BUG at the specified location. This represents a classic case of incomplete validation where data integrity checks are deferred until a later stage, allowing corrupted data to propagate through the system. The call trace demonstrates the execution flow through the block I/O subsystem, indicating that the problem originates from the interaction between the F2FS file system and the kernel's block layer management.
The operational impact of this vulnerability extends beyond simple system instability to potentially enable data corruption and system crashes within F2FS-based storage environments. When exploited, the vulnerability can cause kernel panics that result in system crashes, effectively rendering the affected system unusable until reboot. This type of vulnerability is particularly dangerous in embedded systems, storage servers, or any environment where F2FS is used as the primary file system, as it can lead to complete system outages. The asynchronous nature of the flaw means that the corruption might not be immediately apparent, making it difficult to detect and debug. From an ATT&CK perspective, this vulnerability could be leveraged for denial of service attacks or potentially as a stepping stone for more sophisticated exploitation techniques. The CWE classification for this vulnerability would fall under CWE-119: Improper Access to Memory, as it involves improper handling of memory references during node page validation.
The recommended mitigations for CVE-2026-23265 involve implementing comprehensive node footer validation across all code paths, particularly ensuring that asynchronous node page loading operations perform the same sanity checks as synchronous operations. System administrators should ensure that all F2FS implementations are updated with the patched kernel version that resolves this inconsistency in node page validation. The fix requires modifications to the f2fs_write_end_io() function to enforce consistent validation of node footers regardless of how the node pages were loaded, whether synchronously or asynchronously. Additionally, implementing proper error handling and logging mechanisms can help detect and prevent the propagation of corrupted node pages through the system. Organizations using F2FS should conduct thorough testing of their storage environments to identify any existing corrupted node pages that might trigger this vulnerability during writeback operations. The mitigation strategy should also include monitoring for unusual system behavior that might indicate node page corruption, as this vulnerability can potentially be exploited to cause persistent system instability.