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Fencer Vulns
high 7.8

CVE-2025-40054 json

f2fs: fix UAF issue in f2fs_merge_page_bio()

published 2025-10-28 12 mo ago modified 2026-10-19 20 d ago also EUVD-2025-36474

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 5%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

f2fs: fix UAF issue in f2fs_merge_page_bio()

As JY reported in bugzilla [1],

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 pc : [0xffffffe51d249484] f2fs_is_cp_guaranteed+0x70/0x98 lr : [0xffffffe51d24adbc] f2fs_merge_page_bio+0x520/0x6d4 CPU: 3 UID: 0 PID: 6790 Comm: kworker/u16:3 Tainted: P B W OE 6.12.30-android16-5-maybe-dirty-4k #1 5f7701c9cbf727d1eebe77c89bbbeb3371e895e5 Tainted: [P]=PROPRIETARY_MODULE, [B]=BAD_PAGE, [W]=WARN, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE Workqueue: writeback wb_workfn (flush-254:49) Call trace: f2fs_is_cp_guaranteed+0x70/0x98 f2fs_inplace_write_data+0x174/0x2f4 f2fs_do_write_data_page+0x214/0x81c f2fs_write_single_data_page+0x28c/0x764 f2fs_write_data_pages+0x78c/0xce4 do_writepages+0xe8/0x2fc __writeback_single_inode+0x4c/0x4b4 writeback_sb_inodes+0x314/0x540 __writeback_inodes_wb+0xa4/0xf4 wb_writeback+0x160/0x448 wb_workfn+0x2f0/0x5dc process_scheduled_works+0x1c8/0x458 worker_thread+0x334/0x3f0 kthread+0x118/0x1ac ret_from_fork+0x10/0x20

[1] https://bugzilla.kernel.org/show_bug.cgi?id=220575

The panic was caused by UAF issue w/ below race condition:

kworker - writepages - f2fs_write_cache_pages - f2fs_write_single_data_page - f2fs_do_write_data_page - f2fs_inplace_write_data - f2fs_merge_page_bio - add_inu_page : cache page #1 into bio & cache bio in io->bio_list - f2fs_write_single_data_page - f2fs_do_write_data_page - f2fs_inplace_write_data - f2fs_merge_page_bio - add_inu_page : cache page #2 into bio which is linked in io->bio_list write - f2fs_write_begin : write page #1 - f2fs_folio_wait_writeback - f2fs_submit_merged_ipu_write - f2fs_submit_write_bio : submit bio which inclues page #1 and #2

software IRQ - f2fs_write_end_io - fscrypt_free_bounce_page : freed bounced page which belongs to page #2 - inc_page_count( , WB_DATA_TYPE(data_folio), false) : data_folio points to fio->encrypted_page the bounced page can be freed before accessing it in f2fs_is_cp_guarantee()

It can reproduce w/ below testcase: Run below script in shell #1: for ((i=1;i>0;i++)) do xfs_io -f /mnt/f2fs/enc/file \ -c "pwrite 0 32k" -c "fdatasync"

Run below script in shell #2: for ((i=1;i>0;i++)) do xfs_io -f /mnt/f2fs/enc/file \ -c "pwrite 0 32k" -c "fdatasync"

So, in f2fs_merge_page_bio(), let's avoid using fio->encrypted_page after commit page into internal ipu cache.

Patch / fix

  • Linux Linux 5.10.266, 5.15.217, 6.1.184, 6.6.153, 6.12.105, 6.17.3, 6.18
  • linux Debian 12 6.1.187-1
  • linux Debian 13 6.12.105-1
  • linux Debian 14 6.17.6-1
  • linux-6.12 Debian 12 6.12.107-1~deb12u1

debian advisories DEBIAN-CVE-2025-40054

  • linux Ubuntu 22.04 LTS 5.15.0-202.212
  • linux Ubuntu 25.10 6.17.0-14.14
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1119.126
  • linux-aws Ubuntu 25.10 6.17.0-1007.7
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1120.130
  • linux-gcp Ubuntu 25.10 6.17.0-1007.7
  • linux-gke Ubuntu 22.04 LTS 5.15.0-1115.121
  • linux-ibm Ubuntu 22.04 LTS 5.15.0-1113.117

ubuntu advisories UBUNTU-CVE-2025-40054

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-source-longterm openSUSE Tumbleweed 6.18.16-1.1
  • kernel-source openSUSE Tumbleweed 6.17.7-1.1

opensuse advisories openSUSE-SU-2026:10301-1openSUSE-SU-2025:15702-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-40054 updated

kernel: f2fs: fix UAF issue in f2fs_merge_page_bio()

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.17% chance of exploitation in the next 30 days, higher than 5% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.