# CVE-2026-53300: net: enetc: fix NTMP DMA use-after-free issue

> A use-after-free vulnerability in the Linux kernel enetc driver allows attackers to cause memory corruption or denial of service via DMA operations.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/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:** 26 Jun 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2026-53300, DEBIAN-CVE-2026-53300, GHSA-gcq9-mfq5-gc89, UBUNTU-CVE-2026-53300

## What is CVE-2026-53300?

CVE-2026-53300 is a high-severity use after free vulnerability in Linux kernel, published on 26 Jun 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: enetc: fix NTMP DMA use-after-free issue

The AI-generated review reported a potential DMA use-after-free issue
[1]. If netc_xmit_ntmp_cmd() times out and returns an error, the pending
command is not explicitly aborted, while ntmp_free_data_mem()
unconditionally frees the DMA buffer. If the buffer has already been
reallocated elsewhere, this may lead to silent memory corruption. Because
the hardware eventually processes the pending command and perform a DMA
write of the response to the physical address of the freed buffer.

To resolve this issue, this patch does the following modifications:

1. Convert cbdr->ring_lock from a spinlock to a mutex

The lock was originally a spinlock in case NTMP operations might be
invoked from atomic context. After downstream support for all NTMP
tables, no such usage has materialized. A mutex lock is now required
because the driver now needs to reclaim used BDs and release associated
DMA memory within the lock's context, while dma_free_coherent() might
sleep.

2. Introduce software command BD (struct netc_swcbd)

The hardware write-back overwrites the addr and len fields of the BD,
so the driver cannot rely on the hardware BD to free the associated DMA
memory. The driver now maintains a software shadow BD storing the DMA
buffer pointer, DMA address, and size. And netc_xmit_ntmp_cmd() only
reclaims older BDs when the number of used BDs reaches
NETC_CBDR_CLEAN_WORK (16). The software BD enables correct DMA memory
release. With this, struct ntmp_dma_buf and ntmp_free_data_mem() are no
longer needed and are removed.

3. Require callers to hold ring_lock across netc_xmit_ntmp_cmd()

netc_xmit_ntmp_cmd() releases the ring_lock before the caller finishes
consuming the response. At this point, if a concurrent thread submits
a new command, it may trigger ntmp_clean_cbdr() and free the DMA buffer
while it is still in use. Move ring_lock ownership to the caller to
ensure the response buffer cannot be reclaimed prematurely. So the
helpers ntmp_select_and_lock_cbdr() and ntmp_unlock_cbdr() are added.

These changes eliminate the DMA use-after-free condition and ensure safe
and consistent BD reclamation and DMA buffer lifecycle management.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-53300?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53300?

Apply the vendor's patch.

## Is CVE-2026-53300 being exploited?

There is no known exploitation of CVE-2026-53300 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-2026-53300 and fix it if it is affected.

What it is: CVE-2026-53300 is a high-severity use after free vulnerability in Linux kernel, published on 26 Jun 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-2026-53300 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-2026-53300/ (Markdown: https://insights.sbomify.com/CVE-2026-53300/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53300
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53300
- OSV: https://osv.dev/vulnerability/CVE-2026-53300

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53300/
Summaries are generated and may contain mistakes; the official description above is the record.