# CVE-2026-98986: namespace: remove the fsnotify marks of a mount namespace in process context


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 23 Oct 2026
- **Updated:** 23 Oct 2026
- **Also known as:** BELL-CVE-2026-98986, DEBIAN-CVE-2026-98986, GHSA-6338-gv67-39m8, UBUNTU-CVE-2026-98986

## What is CVE-2026-98986?

CVE-2026-98986 is a vulnerability in Linux, published on 23 Oct 2026. 

### Official description

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

namespace: remove the fsnotify marks of a mount namespace in process context

mnt_ns_release() drops the last passive reference of a mount namespace
and removes its fanotify marks via fsnotify_mntns_delete(). That takes
the mutex of every group with a mark on the namespace and the spinlock
of the connector. Fine from process context. But mnt_ns_tree_remove()
hands the reference the namespace was allocated with to call_rcu() and
so the marks are removed from the RCU softirq:

  BUG: sleeping function called from invalid context at kernel/locking/mutex.c:623
  in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 0, name: swapper/3
   __mutex_lock+0x113/0x24b0
   fsnotify_destroy_marks+0x11b/0x3d0
   mnt_ns_release_rcu+0x57/0xa0
   rcu_core+0x6b6/0x1e40

and lockdep complains about the connector lock being taken from softirq
context. A fanotify group with a FAN_MARK_MNTNS mark on the mount
namespace of another task is all that's needed. Root in a user
namespace can do that for a mount namespace it owns. The task exits and
the namespace is freed with the mark still on it.

Remove the marks in free_mnt_ns() before the namespace is handed to RCU.
That runs in process context once the last active reference is gone. A
mark is added through a file descriptor to the namespace which holds an
active reference so no mark can show up after that.

## Which versions are affected by CVE-2026-98986?


## How do I fix CVE-2026-98986?

Upgrade to a fixed version.

## Is CVE-2026-98986 being exploited?

There is no known exploitation of CVE-2026-98986 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98986 and fix it if it is affected.

What it is: CVE-2026-98986 is a vulnerability in Linux, published on 23 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-98986 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-2026-98986/ (Markdown: https://insights.sbomify.com/CVE-2026-98986/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98986
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98986
- OSV: https://osv.dev/vulnerability/CVE-2026-98986

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98986/
Summaries are generated and may contain mistakes; the official description above is the record.