CVE-2026-89723
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk6th percentile - higher than 6% of all known CVEs
Summary
A slab-out-of-bounds vulnerability was fixed in the Linux kernel's nilfs_direct_propagate() function in the nilfs2 filesystem. After truncating a file, a B-tree node block remained in the cache in a dirty state and was later incorrectly processed as a direct mapping entry, causing an out-of-bounds memory access. The issue was resolved by adding a nilfs_btree_discard() operation to delete the orphaned node block during mapping conversion.
Risk Assessment
The flaw can cause kernel memory corruption, system crash (panic), or potentially be exploited by a local user for privilege escalation. It affects systems with a mounted nilfs2 filesystem.
Recommendation
Update the Linux kernel to a version containing the fix for CVE-2026-89723. If nilfs2 is not in use, consider disabling or unmounting it to reduce exposure.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: nilfs2: fix slab-out-of-bounds in nilfs_direct_propagate after truncation Shuangpeng Bai reported that KASAN detected a slab-out-of-bounds error in nilfs_direct_propagate() during testing. Analysis revealed that after truncating a file, a node block immediately below the B-tree root was not deleted. Instead, it remained in the B-tree node cache in a dirty state. The log writer subsequently detected this block and incorrectly invoked nilfs_direct_propagate() on it, which is designed to handle only data blocks in direct mapping. B-tree nodes in the cache are managed by virtual block numbers, and their logical keys typically exceed the range expected by direct mapping. Consequently, processing such a node as a direct mapping entry triggers a slab-out-of-bounds access. The root cause is that when a B-tree mapping collapses into a direct mapping during truncation, an intermediate node block pointed to by the root node is left behind as garbage instead of being explicitly deleted. This resolves the issue by adding a nilfs_btree_discard() operation to delete the remaining intermediate node block during the conversion. A 'deform' flag is added to the bop_delete interface to explicitly signal that the deletion is part of a mapping transformation. This allows the B-tree mapping implementation to perform the necessary cleanup and discarding of the residual node structure that would be otherwise be left orphaned after the transition.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS