# CVE-2026-90247: bpf: Fix mmap_lock leak in irq_work path

> A race condition in the Linux kernel BPF subsystem can leak mmap locks, causing a denial of service by blocking memory management operations.

- **Severity:** Not scored
- **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-102864, BELL-CVE-2026-90247, DEBIAN-CVE-2026-90247, GHSA-m447-wf7w-9qp4, UBUNTU-CVE-2026-90247

## What is CVE-2026-90247?

CVE-2026-90247 is a denial of service 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:

bpf: Fix mmap_lock leak in irq_work path

stack_map_get_build_id_offset() introduced a per-CPU irq_work to defer
mmap_read_unlock() from NMI context, and bpf_find_vma() later reused the
same mmap_unlock_work. Both callers only check whether the work is busy
before taking mmap_lock, so a nested caller can reuse the slot before the
first caller queues it. Two read locks may then be acquired while only one
deferred unlock runs, leaking a read lock and blocking exit_mmap().

Reserve the per-CPU slot before mmap_read_trylock(). Use the same wrapper
in stackmap and bpf_find_vma() so both callers release the reservation on
trylock failure. Keep rejecting the slot while the irq_work remains busy.
Release it after the irq_work callback unlocks the mm.

## Which versions are affected by CVE-2026-90247?


## How do I fix CVE-2026-90247?

Apply the vendor's patch.

## Is CVE-2026-90247 being exploited?

There is no known exploitation of CVE-2026-90247 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90247 and fix it if it is affected.

What it is: CVE-2026-90247 is a denial of service 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-2026-90247 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-2026-90247/ (Markdown: https://insights.sbomify.com/CVE-2026-90247/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90247
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90247
- OSV: https://osv.dev/vulnerability/CVE-2026-90247

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90247/
Summaries are generated and may contain mistakes; the official description above is the record.