# CVE-2026-98119: netfs: break unbuffered write when netfs_alloc_subrequest() fails

> A local attacker can trigger a kernel crash via null pointer dereference in the netfs subsystem during unbuffered writes when memory allocation fails.

- **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:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-98119, DEBIAN-CVE-2026-98119, GHSA-9vr4-4r2h-jqv2, UBUNTU-CVE-2026-98119

## What is CVE-2026-98119?

CVE-2026-98119 is a medium-severity vulnerability in Linux kernel, published on 25 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:

netfs: break unbuffered write when netfs_alloc_subrequest() fails

syzbot reported a null-ptr-deref below [1] following a fault injection in
netfs_alloc_subrequest(). [0]

When netfs_alloc_subrequest() fails, subreq is NULL.
Later, netfs_prepare_write() tries to initialize members of
subreq(e.g., source), the issue in [1] is triggered.

Let's handle the error of netfs_prepare_write() properly.

[0]
FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 0, space 0, times 0
Call Trace:
 netfs_alloc_subrequest+0x116/0x3f0
 netfs_prepare_write+0x76/0x7b0
 netfs_unbuffered_write+0x75c/0x2020
 netfs_unbuffered_write_iter_locked+0x7d6/0xa80
 netfs_unbuffered_write_iter+0x442/0x720
 v9fs_file_write_iter+0xbf/0x100
 vfs_write+0x6ac/0x1050

[1]
KASAN: null-ptr-deref in range [0x00000000000000a8-0x00000000000000af]
RIP: 0010:netfs_prepare_write+0xbc/0x7b0 fs/netfs/write_issue.c:173
Call Trace:
 netfs_unbuffered_write+0x75c/0x2020 fs/netfs/direct_write.c:111
 netfs_unbuffered_write_iter_locked+0x7d6/0xa80 fs/netfs/direct_write.c:290
 netfs_unbuffered_write_iter+0x442/0x720 fs/netfs/direct_write.c:382
 v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409
 new_sync_write fs/read_write.c:595 [inline]

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-98119?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-98119?

Apply the vendor's patch.

## Is CVE-2026-98119 being exploited?

There is no known exploitation of CVE-2026-98119 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-2026-98119 and fix it if it is affected.

What it is: CVE-2026-98119 is a medium-severity vulnerability in Linux kernel, published on 25 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-2026-98119 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-2026-98119/ (Markdown: https://insights.sbomify.com/CVE-2026-98119/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98119
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98119
- OSV: https://osv.dev/vulnerability/CVE-2026-98119

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98119/
Summaries are generated and may contain mistakes; the official description above is the record.