# CVE-2023-53513: nbd: fix incomplete validation of ioctl arg

> A local attacker can trigger a signed integer overflow in the Linux kernel NBD driver via a crafted ioctl argument, causing a system crash.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 1 Oct 2025
- **Updated:** 11 Jun 2026
- **Also known as:** BELL-CVE-2023-53513, DEBIAN-CVE-2023-53513, GHSA-jvcg-848p-wjgf, ROOT-OS-DEBIAN-11-CVE-2023-53513, UBUNTU-CVE-2023-53513

## What is CVE-2023-53513?

CVE-2023-53513 is a medium-severity vulnerability in Linux kernel, published on 1 Oct 2025. 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:

nbd: fix incomplete validation of ioctl arg

We tested and found an alarm caused by nbd_ioctl arg without verification.
The UBSAN warning calltrace like below:

UBSAN: Undefined behaviour in fs/buffer.c:1709:35
signed integer overflow:
-9223372036854775808 - 1 cannot be represented in type 'long long int'
CPU: 3 PID: 2523 Comm: syz-executor.0 Not tainted 4.19.90 #1
Hardware name: linux,dummy-virt (DT)
Call trace:
 dump_backtrace+0x0/0x3f0 arch/arm64/kernel/time.c:78
 show_stack+0x28/0x38 arch/arm64/kernel/traps.c:158
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x170/0x1dc lib/dump_stack.c:118
 ubsan_epilogue+0x18/0xb4 lib/ubsan.c:161
 handle_overflow+0x188/0x1dc lib/ubsan.c:192
 __ubsan_handle_sub_overflow+0x34/0x44 lib/ubsan.c:206
 __block_write_full_page+0x94c/0xa20 fs/buffer.c:1709
 block_write_full_page+0x1f0/0x280 fs/buffer.c:2934
 blkdev_writepage+0x34/0x40 fs/block_dev.c:607
 __writepage+0x68/0xe8 mm/page-writeback.c:2305
 write_cache_pages+0x44c/0xc70 mm/page-writeback.c:2240
 generic_writepages+0xdc/0x148 mm/page-writeback.c:2329
 blkdev_writepages+0x2c/0x38 fs/block_dev.c:2114
 do_writepages+0xd4/0x250 mm/page-writeback.c:2344

The reason for triggering this warning is __block_write_full_page()
-> i_size_read(inode) - 1 overflow.
inode->i_size is assigned in __nbd_ioctl() -> nbd_set_size() -> bytesize.
We think it is necessary to limit the size of arg to prevent errors.

Moreover, __nbd_ioctl() -> nbd_add_socket(), arg will be cast to int.
Assuming the value of arg is 0x80000000000000001) (on a 64-bit machine),
it will become 1 after the coercion, which will return unexpected results.

Fix it by adding checks to prevent passing in too large numbers.

Weakness: CWE-674 (Uncontrolled Recursion)

## Which versions are affected by CVE-2023-53513?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2023-53513?

Apply the vendor's patch.

## Is CVE-2023-53513 being exploited?

There is no known exploitation of CVE-2023-53513 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-2023-53513 and fix it if it is affected.

What it is: CVE-2023-53513 is a medium-severity vulnerability in Linux kernel, published on 1 Oct 2025. 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-2023-53513 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-2023-53513/ (Markdown: https://insights.sbomify.com/CVE-2023-53513/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-53513
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-53513
- OSV: https://osv.dev/vulnerability/CVE-2023-53513

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-53513/
Summaries are generated and may contain mistakes; the official description above is the record.