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Fencer Vulns
no cvss —

CVE-2026-23181 json

btrfs: sync read disk super and set block size

published 2026-02-14 8 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-6110

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 7%
public exploits
0
none known

Summary

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

btrfs: sync read disk super and set block size

When the user performs a btrfs mount, the block device is not set correctly. The user sets the block size of the block device to 0x4000 by executing the BLKBSZSET command. Since the block size change also changes the mapping->flags value, this further affects the result of the mapping_min_folio_order() calculation.

Let's analyze the following two scenarios:

Scenario 1: Without executing the BLKBSZSET command, the block size is 0x1000, and mapping_min_folio_order() returns 0;

Scenario 2: After executing the BLKBSZSET command, the block size is 0x4000, and mapping_min_folio_order() returns 2.

do_read_cache_folio() allocates a folio before the BLKBSZSET command is executed. This results in the allocated folio having an order value of 0. Later, after BLKBSZSET is executed, the block size increases to 0x4000, and the mapping_min_folio_order() calculation result becomes 2.

This leads to two undesirable consequences:

1. filemap_add_folio() triggers a VM_BUG_ON_FOLIO(folio_order(folio) < mapping_min_folio_order(mapping)) assertion.

2. The syzbot report [1] shows a null pointer dereference in create_empty_buffers() due to a buffer head allocation failure.

Synchronization should be established based on the inode between the BLKBSZSET command and read cache page to prevent inconsistencies in block size or mapping flags before and after folio allocation.

[1] KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:create_empty_buffers+0x4d/0x480 fs/buffer.c:1694 Call Trace: folio_create_buffers+0x109/0x150 fs/buffer.c:1802 block_read_full_folio+0x14c/0x850 fs/buffer.c:2403 filemap_read_folio+0xc8/0x2a0 mm/filemap.c:2496 do_read_cache_folio+0x266/0x5c0 mm/filemap.c:4096 do_read_cache_page mm/filemap.c:4162 [inline] read_cache_page_gfp+0x29/0x120 mm/filemap.c:4195 btrfs_read_disk_super+0x192/0x500 fs/btrfs/volumes.c:1367

Patch / fix

  • Linux Linux 6.18.10, 6.19
  • linux Debian 14 6.18.10-1

debian advisories DEBIAN-CVE-2026-23181

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-2026-23181 updated cvss 4.7

kernel: btrfs: sync read disk super and set block size

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 10 kernel
    affected: no fix available “Fix deferred”
  • 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
    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

0.18% chance of exploitation in the next 30 days, higher than 7% of all scored CVEs (FIRST EPSS, 2026-11-08).

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.