# CVE-2026-45915: fat: avoid parent link count underflow in rmdir

> A corrupted FAT image can cause an integer underflow in the Linux kernel's rmdir operation, leading to a system crash or denial of service.

- **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:** 27 May 2026
- **Updated:** 27 May 2026
- **Also known as:** BELL-CVE-2026-45915, DEBIAN-CVE-2026-45915, GHSA-2qhg-8p2v-wf99, ROOT-OS-UBUNTU-2204-CVE-2026-45915, ROOT-OS-UBUNTU-2404-CVE-2026-45915, UBUNTU-CVE-2026-45915

## What is CVE-2026-45915?

CVE-2026-45915 is a medium-severity vulnerability in Linux kernel, published on 27 May 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:

fat: avoid parent link count underflow in rmdir

Corrupted FAT images can leave a directory inode with an incorrect
i_nlink (e.g. 2 even though subdirectories exist). rmdir then
unconditionally calls drop_nlink(dir) and can drive i_nlink to 0,
triggering the WARN_ON in drop_nlink().

Add a sanity check in vfat_rmdir() and msdos_rmdir(): only drop the
parent link count when it is at least 3, otherwise report a filesystem
error.

## Which versions are affected by CVE-2026-45915?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-45915?

Apply the vendor's patch.

## Is CVE-2026-45915 being exploited?

There is no known exploitation of CVE-2026-45915 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-2026-45915 and fix it if it is affected.

What it is: CVE-2026-45915 is a medium-severity vulnerability in Linux kernel, published on 27 May 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-2026-45915 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-2026-45915/ (Markdown: https://insights.sbomify.com/CVE-2026-45915/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45915
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45915
- OSV: https://osv.dev/vulnerability/CVE-2026-45915

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45915/
Summaries are generated and may contain mistakes; the official description above is the record.