# CVE-2026-99175: fsnotify: prevent mark additions during connector teardown


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** AZL-111329, BELL-CVE-2026-99175, DEBIAN-CVE-2026-99175, GHSA-qvp9-6wr3-29m5, UBUNTU-CVE-2026-99175

## What is CVE-2026-99175?

CVE-2026-99175 is a vulnerability in Linux, published on 28 Oct 2026. 

### Official description

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

fsnotify: prevent mark additions during connector teardown

fsnotify_destroy_marks() keeps a reference to its current mark while it
drops conn->lock to destroy the mark. This stabilizes the forward-walk
cursor, but does not prevent a new mark from being inserted before it.
For example, an inotify watch re-added after IN_IGNORED sorts before the
old, detached mark for the same group. The walk can miss the replacement
and then detach the entire connector from the object.

The replacement is still on its group's marks_list and, for inotify, in
the watch IDR. The group mutex no longer protects the connector's object
from disappearing. An unprivileged fdinfo read racing the final detach
can consequently call igrab(NULL):

  BUG: KASAN: null-ptr-deref in igrab+0x24/0x100
  Write of size 4 at addr 0000000000000148
  Call Trace:
   igrab+0x24/0x100
   inotify_show_fdinfo+0x1dc/0x5e0
   seq_show+0x397/0x690

Set a DESTROYING flag under conn->lock before starting the walk, and
reject new marks on that connector with -ENOENT. The existing add-mark
error paths undo the temporary group-list entry and the backend's watch
allocation. Do not wait for teardown while holding the group mutex,
which the destroyer needs. Once the old connector is detached, an add
can install a fresh connector as before.

This closes the insertion race for all object types using the common
connector teardown, without changing the mark reference or SRCU lifetime
rules.

## Which versions are affected by CVE-2026-99175?


## How do I fix CVE-2026-99175?

Upgrade to a fixed version.

## Is CVE-2026-99175 being exploited?

There is no known exploitation of CVE-2026-99175 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99175 and fix it if it is affected.

What it is: CVE-2026-99175 is a vulnerability in Linux, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99175 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-2026-99175/ (Markdown: https://insights.sbomify.com/CVE-2026-99175/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99175
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99175
- OSV: https://osv.dev/vulnerability/CVE-2026-99175

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99175/
Summaries are generated and may contain mistakes; the official description above is the record.