# CVE-2026-46251: btrfs: fix block_group_tree dirty_list corruption

> A memory corruption vulnerability in the Linux kernel's btrfs filesystem allows attackers to cause system crashes or potentially execute code when specific features are enabled.

- **Severity:** High 8.4 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 3 Jun 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2026-46251, DEBIAN-CVE-2026-46251, GHSA-c5jw-wr2h-vpj4, UBUNTU-CVE-2026-46251

## What is CVE-2026-46251?

CVE-2026-46251 is a high-severity memory corruption vulnerability in Linux kernel, published on 3 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

btrfs: fix block_group_tree dirty_list corruption

When the incompat flag EXTENT_TREE_V2 is set, we unconditionally add the
block group tree to the switch_commits list before calling
switch_commit_roots, as we do for the tree root and the chunk root.
However, the block group tree uses normal root dirty tracking and in any
transaction that does an allocation and dirties a block group, the block
group root will already be linked to a list by the dirty_list field and
this use of list_add_tail() is invalid and corrupts the prev/next
members of block_group_root->dirty_list.

This is apparent on a subsequent list_del on the prev if we enable
CONFIG_DEBUG_LIST:

  [32.1571] ------------[ cut here ]------------
  [32.1572] list_del corruption. next->prev should beffff958890202538, but was ffff9588992bd538. (next=ffff958890201538)
  [32.1575] WARNING: lib/list_debug.c:65 at 0x0, CPU#3: sync/607
  [32.1583] CPU: 3 UID: 0 PID: 607 Comm: sync Not tainted 6.18.0 #24PREEMPT(none)
  [32.1585] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS1.17.0-4.fc41 04/01/2014
  [32.1587] RIP: 0010:__list_del_entry_valid_or_report+0x108/0x120
  [32.1593] RSP: 0018:ffffaa288287fdd0 EFLAGS: 00010202
  [32.1594] RAX: 0000000000000001 RBX: ffff95889326e800 RCX:ffff958890201538
  [32.1596] RDX: ffff9588992bd538 RSI: ffff958890202538 RDI:ffffffff82a41e00
  [32.1597] RBP: ffff958890202538 R08: ffffffff828fc1e8 R09:00000000ffffefff
  [32.1599] R10: ffffffff8288c200 R11: ffffffff828e4200 R12:ffff958890201538
  [32.1601] R13: ffff95889326e958 R14: ffff958895c24000 R15:ffff958890202538
  [32.1603] FS:  00007f0c28eb5740(0000) GS:ffff958af2bd2000(0000)knlGS:0000000000000000
  [32.1605] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [32.1607] CR2: 00007f0c28e8a3cc CR3: 0000000109942005 CR4:0000000000370ef0
  [32.1609] Call Trace:
  [32.1610]  <TASK>
  [32.1611]  switch_commit_roots+0x82/0x1d0 [btrfs]
  [32.1615]  btrfs_commit_transaction+0x968/0x1550 [btrfs]
  [32.1618]  ? btrfs_attach_transaction_barrier+0x23/0x60 [btrfs]
  [32.1621]  __iterate_supers+0xe8/0x190
  [32.1622]  ? __pfx_sync_fs_one_sb+0x10/0x10
  [32.1623]  ksys_sync+0x63/0xb0
  [32.1624]  __do_sys_sync+0xe/0x20
  [32.1625]  do_syscall_64+0x73/0x450
  [32.1626]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
  [32.1627] RIP: 0033:0x7f0c28d05d2b
  [32.1632] RSP: 002b:00007ffc9d988048 EFLAGS: 00000246 ORIG_RAX:00000000000000a2
  [32.1634] RAX: ffffffffffffffda RBX: 00007ffc9d988228 RCX:00007f0c28d05d2b
  [32.1636] RDX: 00007f0c28e02301 RSI: 00007ffc9d989b21 RDI:00007f0c28dba90d
  [32.1637] RBP: 0000000000000001 R08: 0000000000000001 R09:0000000000000000
  [32.1639] R10: 0000000000000000 R11: 0000000000000246 R12:000055b96572cb80
  [32.1641] R13: 000055b96572b19f R14: 00007f0c28dfa434 R15:000055b96572b034
  [32.1643]  </TASK>
  [32.1644] irq event stamp: 0
  [32.1644] hardirqs last  enabled at (0): [<0000000000000000>] 0x0
  [32.1646] hardirqs last disabled at (0): [<ffffffff81298817>]copy_process+0xb37/0x2260
  [32.1648] softirqs last  enabled at (0): [<ffffffff81298817>]copy_process+0xb37/0x2260
  [32.1650] softirqs last disabled at (0): [<0000000000000000>] 0x0
  [32.1652] ---[ end trace 0000000000000000 ]---

Furthermore, this list corruption eventually (when we happen to add a
new block group) results in getting the switch_commits and
dirty_cowonly_roots lists mixed up and attempting to call update_root
on the tree root which can't be found in the tree root, resulting in a
transaction abort:

  [87.8269] BTRFS critical (device nvme1n1): unable to find root key (1 0 0) in tree 1
  [87.8272] ------------[ cut here ]------------
  [87.8274] BTRFS: Transaction aborted (error -117)
  [87.8275] WARNING: fs/btrfs/root-tree.c:153 at 0x0, CPU#4: sync/703
  [87.8285] CPU: 4 UID: 0 PID: 703 Comm: sync Not tainted 6.18.0 #25 PREEMPT(none)
  [87.8287] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.17.0-4.fc41 0
---truncated---

## Which versions are affected by CVE-2026-46251?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-46251?

Apply the vendor's patch.

## Is CVE-2026-46251 being exploited?

There is no known exploitation of CVE-2026-46251 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-46251 and fix it if it is affected.

What it is: CVE-2026-46251 is a high-severity memory corruption vulnerability in Linux kernel, published on 3 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-46251 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-46251/ (Markdown: https://insights.sbomify.com/CVE-2026-46251/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46251
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46251
- OSV: https://osv.dev/vulnerability/CVE-2026-46251

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46251/
Summaries are generated and may contain mistakes; the official description above is the record.