# CVE-2026-98126: smb/client: validate new EOF for zero range

> A local attacker can bypass file size limits on CIFS mounts, potentially causing resource exhaustion or privilege escalation.

- **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:** 21 Oct 2026
- **Also known as:** AZL-104511, BELL-CVE-2026-98126, DEBIAN-CVE-2026-98126, GHSA-788x-356f-432m, UBUNTU-CVE-2026-98126

## What is CVE-2026-98126?

CVE-2026-98126 is a medium-severity missing authorization 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:

smb/client: validate new EOF for zero range

When FALLOC_FL_ZERO_RANGE is used without FALLOC_FL_KEEP_SIZE,
smb3_zero_range() may extend EOF without checking RLIMIT_FSIZE, allowing
the file to grow beyond the caller's file-size limit.

Fix this by calling inode_newsize_ok() before sending the zero-range
request when the operation would extend EOF.

Reproducer, using a file on a CIFS mount:

	bash -c '
	        FILE=/mnt/cifs/repro

	        trap "" SIGXFSZ
	        ulimit -f 3072

	        truncate -s 2M "$FILE"
	        fallocate --zero-range -o 0 -l 4M "$FILE"
	        echo "fallocate rc=$?"
	        stat -c "file size=%s" "$FILE"
	'

Before this change, the operation succeeds despite the 3 MiB limit:

	fallocate rc=0
	file size=4194304

After this change, fallocate fails and leaves the file at 2 MiB.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-98126?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-98126?

Apply the vendor's patch.

## Is CVE-2026-98126 being exploited?

There is no known exploitation of CVE-2026-98126 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-2026-98126 and fix it if it is affected.

What it is: CVE-2026-98126 is a medium-severity missing authorization 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-2026-98126 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-2026-98126/ (Markdown: https://insights.sbomify.com/CVE-2026-98126/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98126
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98126
- OSV: https://osv.dev/vulnerability/CVE-2026-98126

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98126/
Summaries are generated and may contain mistakes; the official description above is the record.