CyberSecBulletin
CVE-2026-31715NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-31715 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 7dbdab4430e4654db9aacef12b9b3b8b29ca25cb, ffb94770dbdfb5411be5d9f44a960b010ec890ad, 0d40b26377f891e6dcb6efaf8ef9374c99be1b1d as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.12% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 7dbdab4430e4654db9aacef12b9b3b8b29ca25cb or ffb94770dbdfb5411be5d9f44a960b010ec890ad or 0d40b26377f891e6dcb6efaf8ef9374c99be1b1d or 1171f329cf1c175321251ac40fd126150d7ad1e8, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.18.25 or 7.0.2, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux50fa53eccf9f911a5b435248a2b0bd484fd82e5e up to, but not including, 7dbdab4430e4654db9aacef12b9b3b8b29ca25cb; 50fa53eccf9f911a5b435248a2b0bd484fd82e5e up to, but not including, ffb94770dbdfb5411be5d9f44a960b010ec890ad; 50fa53eccf9f911a5b435248a2b0bd484fd82e5e up to, but not including, 0d40b26377f891e6dcb6efaf8ef9374c99be1b1d; 50fa53eccf9f911a5b435248a2b0bd484fd82e5e up to, but not including, 1171f329cf1c175321251ac40fd126150d7ad1e8; 50fa53eccf9f911a5b435248a2b0bd484fd82e5e up to, but not including, 7be222de96c0f9eee6e65eeb017ef855ee185cfa; 50fa53eccf9f911a5b435248a2b0bd484fd82e5e up to, but not including, 963d2e24d9d92a31e6773b0f642214f10013ebf7; 50fa53eccf9f911a5b435248a2b0bd484fd82e5e up to, but not including, 188bb65f247a7a7c62f287c9a263aee3cad96fa5; 50fa53eccf9f911a5b435248a2b0bd484fd82e5e up to, but not including, 2d9c4a4ed4eef1f82c5b16b037aee8bad819fd53; and 1 more ranges7dbdab4430e4654db9aacef12b9b3b8b29ca25cb, ffb94770dbdfb5411be5d9f44a960b010ec890ad, 0d40b26377f891e6dcb6efaf8ef9374c99be1b1d, 1171f329cf1c175321251ac40fd126150d7ad1e8, 7be222de96c0f9eee6e65eeb017ef855ee185cfa, 963d2e24d9d92a31e6773b0f642214f10013ebf7
LinuxLinux Kernel4.19 up to, but not including, 6.18.25; 6.19 up to, but not including, 7.0.2; 7.16.18.25, 7.0.2

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Official description

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix UAF caused by decrementing sbi->nr_pages[] in f2fs_write_end_io() The xfstests case "generic/107" and syzbot have both reported a NULL pointer dereference. The concurrent scenario that triggers the panic is as follows: F2FS_WB_CP_DATA write callback umount - f2fs_write_checkpoint - f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA) - blk_mq_end_request - bio_endio - f2fs_write_end_io : dec_page_count(sbi, F2FS_WB_CP_DATA) : wake_up(&sbi->cp_wait) - kill_f2fs_super - kill_block_super - f2fs_put_super : iput(sbi->node_inode) : sbi->node_inode = NULL : f2fs_in_warm_node_list - is_node_folio // sbi->node_inode is NULL and panic The root cause is that f2fs_put_super() calls iput(sbi->node_inode) and sets sbi->node_inode to NULL after sbi->nr_pages[F2FS_WB_CP_DATA] is decremented to zero. As a result, f2fs_in_warm_node_list() may dereference a NULL node_inode when checking whether a folio belongs to the node inode, leading to a panic. This patch fixes the issue by calling f2fs_in_warm_node_list() before decrementing sbi->nr_pages[F2FS_WB_CP_DATA], thus preventing the use-after-free condition.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Use After Free

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

How developers prevent this class of flaw

  • Choose a language that provides automatic memory management.
  • When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.

More Use After Free vulnerabilities (CWE-416)

Timeline

  1. CVE record published.
  2. Record last changed materially (score, affected products, status or references).

References

Recent Use After Free vulnerabilities

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