# CVE-2026-63819: f2fs: fix to do sanity check on f2fs_get_node_folio_ra()

> A missing sanity check in the f2fs filesystem allows a local attacker to trigger a kernel bug and crash the system via a crafted mount operation.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Jul 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-63819, DEBIAN-CVE-2026-63819, GHSA-x28c-5hrw-xmh5, ROOT-OS-DEBIAN-11-CVE-2026-63819, ROOT-OS-DEBIAN-12-CVE-2026-63819, ROOT-OS-DEBIAN-13-CVE-2026-63819, ROOT-OS-UBUNTU-2204-CVE-2026-63819, UBUNTU-CVE-2026-63819

## What is CVE-2026-63819?

CVE-2026-63819 is a high-severity denial of service vulnerability in Linux, published on 19 Jul 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:

f2fs: fix to do sanity check on f2fs_get_node_folio_ra()

kernel BUG at fs/f2fs/file.c:845!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5336 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:f2fs_do_truncate_blocks+0x1115/0x1140 fs/f2fs/file.c:845
Code: fc fc 90 0f 0b e8 8b 9d 9a fd 90 0f 0b e8 83 9d 9a fd 48 89 df 48 c7 c6 60 d1 1a 8c e8 54 f1 fc fc 90 0f 0b e8 6c 9d 9a fd 90 <0f> 0b e8 64 9d 9a fd 90 0f 0b 90 e9 93 fd ff ff e8 56 9d 9a fd 90
RSP: 0018:ffffc9000e4474c0 EFLAGS: 00010283
RAX: ffffffff842b1d34 RBX: 0000000000000003 RCX: 0000000000100000
RDX: ffffc9000f03a000 RSI: 0000000000035503 RDI: 0000000000035504
RBP: ffffc9000e447608 R08: ffff8880123b0000 R09: 0000000000000002
R10: 00000000fffffffe R11: 0000000000000002 R12: 0000000000000001
R13: 0000000000000000 R14: 1ffff92001c88ea0 R15: 00000000ffff039c
FS:  00007f7e02ee36c0(0000) GS:ffff88808c887000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff0305c4000 CR3: 0000000012d4c000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 f2fs_truncate_blocks+0x10a/0x300 fs/f2fs/file.c:882
 f2fs_truncate+0x471/0x7c0 fs/f2fs/file.c:940
 f2fs_evict_inode+0xa3f/0x1ac0 fs/f2fs/inode.c:907
 evict+0x61e/0xb10 fs/inode.c:841
 f2fs_fill_super+0x5f43/0x78f0 fs/f2fs/super.c:5224
 get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694
 vfs_get_tree+0x92/0x2a0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3758 [inline]
 do_new_mount+0x341/0xd30 fs/namespace.c:3834
 do_mount fs/namespace.c:4167 [inline]
 __do_sys_mount fs/namespace.c:4383 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4360
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

	count = ADDRS_PER_PAGE(dn.node_folio, inode);

	count -= dn.ofs_in_node;
	f2fs_bug_on(sbi, count < 0);

The fuzz test will trigger above bug_on in f2fs.

The root cause should be: in the corrupted inode, there is a direct node
which has the same ino and nid in its footer, so in f2fs_do_truncate_blocks(),
after f2fs_get_dnode_of_data() finds such dnode:
1) ADDRS_PER_PAGE(dn.node_folio, inode) will return 923
2) once dn.ofs_in_node points to addr[923, 1017]
Then it will trigger the system panic.

Let's introduce NODE_TYPE_NON_IXNODE to indicate current node should
not be an inode or xattr node, and then use it in below path to detect
inconsistent node chain in inode mapping table:

- f2fs_do_truncate_blocks
 - f2fs_get_dnode_of_data
  - f2fs_get_node_folio_ra
   -  __get_node_folio
    - f2fs_sanity_check_node_footer
     - case NODE_TYPE_NON_IXNODE -> check whether it is inode|xnode

## Which versions are affected by CVE-2026-63819?


## How do I fix CVE-2026-63819?

Apply the vendor's patch.

## Is CVE-2026-63819 being exploited?

There is no known exploitation of CVE-2026-63819 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63819 and fix it if it is affected.

What it is: CVE-2026-63819 is a high-severity denial of service vulnerability in Linux, published on 19 Jul 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-2026-63819 in the wild and no public exploit code.

Affected product: Linux. 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-2026-63819/ (Markdown: https://insights.sbomify.com/CVE-2026-63819/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63819
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63819
- OSV: https://osv.dev/vulnerability/CVE-2026-63819

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63819/
Summaries are generated and may contain mistakes; the official description above is the record.