CVE-2026-89723: Linux Vulnerability (CVSS 7.8)

Description

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.

Metrics

CVSS 3.1

7.8/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

0.16%

5.8th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 36a580eb489f54d81a0534974962e732a314b999, < 39005fd1ce654ffdecacddc406b9a038efe606e6; >= 36a580eb489f54d81a0534974962e732a314b999, < bf49e6f6ddc12445a0330708b365de6458085980; >= 36a580eb489f54d81a0534974962e732a314b999, < 4a1bb1f9f24a935c9b3f4fbf98012fa6d4ad826d; >= 36a580eb489f54d81a0534974962e732a314b999, < b313edfbc0c2a60f7ce09b2e81ee71909ab8ddaf; >= 36a580eb489f54d81a0534974962e732a314b999, < 5d3783c451a546373662ee11ec17019273e68034; >= 36a580eb489f54d81a0534974962e732a314b999, < 448636c745a3f3b8582a0b8ce718c890a11c0fa9; >= 36a580eb489f54d81a0534974962e732a314b999, < 28362e8ce51377afdec1782e661e808328a10514; >= 36a580eb489f54d81a0534974962e732a314b999, < 45662dedb8f272ef7f16e69f13424c4bd0399240
Linux	Linux	2.6.30

References

Timeline

Published: Sep 11, 2026
Last Modified: Sep 14, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-89723?

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.

How severe is CVE-2026-89723?

CVE-2026-89723 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 0.16% probability of exploitation in the next 30 days.

How do I fix CVE-2026-89723?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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