# CVE-2026-90291: module/dups: Fix use-after-free in kmod_dup_req lifetime handling

> A use-after-free in the Linux kernel module duplication code allows attackers to execute arbitrary code or escalate privileges.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 17 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-101870, BELL-CVE-2026-90291, DEBIAN-CVE-2026-90291, GHSA-hjw3-fxm2-vph2, UBUNTU-CVE-2026-90291

## What is CVE-2026-90291?

CVE-2026-90291 is a high-severity use after free vulnerability in Linux, published on 17 Sep 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:

module/dups: Fix use-after-free in kmod_dup_req lifetime handling

The kmod dups code uses RCU to ensure that a kmod_dup_req instance is freed
only after it is no longer referenced. When releasing an instance, the
kmod_dup_request_delete() function removes the kmod_dup_req from the
dup_kmod_reqs list, waits via synchronize_rcu() and finally frees it.
However, this doesn't work correctly because parallel users referencing the
instance in kmod_dup_request_exists_wait() don't enter an RCU read-side
critical section. This can result in a use-after-free.

The kmod_dup_request_exists_wait() function may need to hold a valid
reference to a kmod_dup_req instance across a blocking wait until the
corresponding modprobe command completes. This makes it unsuitable for RCU.

Fix the issue by changing the lifecycle management of kmod_dup_req to use
reference counting.

## Which versions are affected by CVE-2026-90291?


## How do I fix CVE-2026-90291?

Apply the vendor's patch.

## Is CVE-2026-90291 being exploited?

There is no known exploitation of CVE-2026-90291 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90291 and fix it if it is affected.

What it is: CVE-2026-90291 is a high-severity use after free vulnerability in Linux, published on 17 Sep 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-2026-90291 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-2026-90291/ (Markdown: https://insights.sbomify.com/CVE-2026-90291/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90291
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90291
- OSV: https://osv.dev/vulnerability/CVE-2026-90291

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90291/
Summaries are generated and may contain mistakes; the official description above is the record.