# CVE-2026-98027: net: dsa: mv88e6xxx: bound the policy rule dump by the caller's buffer size

> A local user can cause a kernel crash or memory corruption in the Marvell DSA driver by triggering a buffer overflow during policy rule dumps.

- **Severity:** High 7.0 (`CVSS:3.1/AV:L/AC:H/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:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104448, BELL-CVE-2026-98027, DEBIAN-CVE-2026-98027, GHSA-rmvm-8mw4-j874, UBUNTU-CVE-2026-98027

## What is CVE-2026-98027?

CVE-2026-98027 is a high-severity denial of service vulnerability in Linux, 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:

net: dsa: mv88e6xxx: bound the policy rule dump by the caller's buffer size

mv88e6xxx_get_rxnfc() uses rxnfc->rule_cnt as the write index while
dumping the policy IDR, clobbering the input value before it has been
looked at.  That input is the number of entries the caller had room for.
ETHTOOL_GRXCLSRLALL requires no CAP_NET_ADMIN and the ioctl sizes the
buffer from the rule_cnt userspace passes in, so once an admin has
installed policy rules any user can ask for fewer slots than there are
rules and run off the end of the allocation.  A rule_cnt of 0 leaves the
buffer pointer NULL and the walk dereferences it.

Count into a local so the caller's limit survives the walk, and stop with
-EMSGSIZE once it is reached.

## Which versions are affected by CVE-2026-98027?


## How do I fix CVE-2026-98027?

Apply the vendor's patch.

## Is CVE-2026-98027 being exploited?

There is no known exploitation of CVE-2026-98027 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98027 and fix it if it is affected.

What it is: CVE-2026-98027 is a high-severity denial of service vulnerability in Linux, 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-2026-98027 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-2026-98027/ (Markdown: https://insights.sbomify.com/CVE-2026-98027/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98027
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98027
- OSV: https://osv.dev/vulnerability/CVE-2026-98027

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98027/
Summaries are generated and may contain mistakes; the official description above is the record.