# CVE-2026-46040: inotify: fix watch count leak when fsnotify_add_inode_mark_locked() fails

> A resource leak in the Linux kernel inotify subsystem allows attackers to exhaust watch limits, causing 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:** 15 Oct 2026
- **Also known as:** AZL-88467, BELL-CVE-2026-46040, DEBIAN-CVE-2026-46040, GHSA-38g3-xqxq-2v2p, ROOT-OS-DEBIAN-11-CVE-2026-46040, ROOT-OS-DEBIAN-12-CVE-2026-46040, ROOT-OS-UBUNTU-2204-CVE-2026-46040, ROOT-OS-UBUNTU-2404-CVE-2026-46040, UBUNTU-CVE-2026-46040

## What is CVE-2026-46040?

CVE-2026-46040 is a medium-severity denial of service 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:

inotify: fix watch count leak when fsnotify_add_inode_mark_locked() fails

When fsnotify_add_inode_mark_locked() fails in inotify_new_watch(),
the error path calls inotify_remove_from_idr() but does not call
dec_inotify_watches() to undo the preceding inc_inotify_watches().
This leaks a watch count, and repeated failures can exhaust the
max_user_watches limit with -ENOSPC even when no watches are active.

Prior to commit 1cce1eea0aff ("inotify: Convert to using per-namespace
limits"), the watch count was incremented after fsnotify_add_mark_locked()
succeeded, so this path was not affected. The conversion moved
inc_inotify_watches() before the mark insertion without adding the
corresponding rollback.

Add the missing dec_inotify_watches() call in the error path.

## Which versions are affected by CVE-2026-46040?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-46040?

Apply the vendor's patch.

## Is CVE-2026-46040 being exploited?

There is no known exploitation of CVE-2026-46040 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-2026-46040 and fix it if it is affected.

What it is: CVE-2026-46040 is a medium-severity denial of service 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-2026-46040 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-2026-46040/ (Markdown: https://insights.sbomify.com/CVE-2026-46040/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46040
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46040
- OSV: https://osv.dev/vulnerability/CVE-2026-46040

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46040/
Summaries are generated and may contain mistakes; the official description above is the record.