# CVE-2025-37865: net: dsa: mv88e6xxx: fix -ENOENT when deleting VLANs and MST is unsupported

> A Linux kernel bug in the Marvell DSA driver causes a denial of service when deleting VLANs on chips without MST support due to uninitialized memory access.

- **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:** 9 May 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-37865, DEBIAN-CVE-2025-37865, GHSA-89h6-q3w2-mjxm, ROOT-OS-DEBIAN-12-CVE-2025-37865, ROOT-OS-UBUNTU-2404-CVE-2025-37865, UBUNTU-CVE-2025-37865

## What is CVE-2025-37865?

CVE-2025-37865 is a medium-severity vulnerability in Debian Debian Linux, published on 9 May 2025. 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: fix -ENOENT when deleting VLANs and MST is unsupported

Russell King reports that on the ZII dev rev B, deleting a bridge VLAN
from a user port fails with -ENOENT:
https://lore.kernel.org/netdev/Z_lQXNP0s5-IiJzd@shell.armlinux.org.uk/

This comes from mv88e6xxx_port_vlan_leave() -> mv88e6xxx_mst_put(),
which tries to find an MST entry in &chip->msts associated with the SID,
but fails and returns -ENOENT as such.

But we know that this chip does not support MST at all, so that is not
surprising. The question is why does the guard in mv88e6xxx_mst_put()
not exit early:

	if (!sid)
		return 0;

And the answer seems to be simple: the sid comes from vlan.sid which
supposedly was previously populated by mv88e6xxx_vtu_get().
But some chip->info->ops->vtu_getnext() implementations do not populate
vlan.sid, for example see mv88e6185_g1_vtu_getnext(). In that case,
later in mv88e6xxx_port_vlan_leave() we are using a garbage sid which is
just residual stack memory.

Testing for sid == 0 covers all cases of a non-bridge VLAN or a bridge
VLAN mapped to the default MSTI. For some chips, SID 0 is valid and
installed by mv88e6xxx_stu_setup(). A chip which does not support the
STU would implicitly only support mapping all VLANs to the default MSTI,
so although SID 0 is not valid, it would be sufficient, if we were to
zero-initialize the vlan structure, to fix the bug, due to the
coincidence that a test for vlan.sid == 0 already exists and leads to
the same (correct) behavior.

Another option which would be sufficient would be to add a test for
mv88e6xxx_has_stu() inside mv88e6xxx_mst_put(), symmetric to the one
which already exists in mv88e6xxx_mst_get(). But that placement means
the caller will have to dereference vlan.sid, which means it will access
uninitialized memory, which is not nice even if it ignores it later.

So we end up making both modifications, in order to not rely just on the
sid == 0 coincidence, but also to avoid having uninitialized structure
fields which might get temporarily accessed.

Weakness: CWE-908 (Use of Uninitialized Resource)

## Which versions are affected by CVE-2025-37865?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-37865?

Apply the vendor's patch.

## Is CVE-2025-37865 being exploited?

There is no known exploitation of CVE-2025-37865 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

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- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-37865 and fix it if it is affected.

What it is: CVE-2025-37865 is a medium-severity vulnerability in Debian Debian Linux, published on 9 May 2025. 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-2025-37865 in the wild and no public exploit code.

Affected product: Debian Debian 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-2025-37865/ (Markdown: https://insights.sbomify.com/CVE-2025-37865/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-37865
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-37865
- OSV: https://osv.dev/vulnerability/CVE-2025-37865

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-37865/
Summaries are generated and may contain mistakes; the official description above is the record.