# CVE-2025-68232: veth: more robust handing of race to avoid txq getting stuck

> A race condition in the Linux kernel veth driver can cause a permanent TX queue stall, leading to network denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Dec 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-68232, DEBIAN-CVE-2025-68232, GHSA-mrvq-mp59-qvj4, UBUNTU-CVE-2025-68232

## What is CVE-2025-68232?

CVE-2025-68232 is a high-severity vulnerability in Linux, published on 16 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

veth: more robust handing of race to avoid txq getting stuck

Commit dc82a33297fc ("veth: apply qdisc backpressure on full ptr_ring to
reduce TX drops") introduced a race condition that can lead to a permanently
stalled TXQ. This was observed in production on ARM64 systems (Ampere Altra
Max).

The race occurs in veth_xmit(). The producer observes a full ptr_ring and
stops the queue (netif_tx_stop_queue()). The subsequent conditional logic,
intended to re-wake the queue if the consumer had just emptied it (if
(__ptr_ring_empty(...)) netif_tx_wake_queue()), can fail. This leads to a
"lost wakeup" where the TXQ remains stopped (QUEUE_STATE_DRV_XOFF) and
traffic halts.

This failure is caused by an incorrect use of the __ptr_ring_empty() API
from the producer side. As noted in kernel comments, this check is not
guaranteed to be correct if a consumer is operating on another CPU. The
empty test is based on ptr_ring->consumer_head, making it reliable only for
the consumer. Using this check from the producer side is fundamentally racy.

This patch fixes the race by adopting the more robust logic from an earlier
version V4 of the patchset, which always flushed the peer:

(1) In veth_xmit(), the racy conditional wake-up logic and its memory barrier
are removed. Instead, after stopping the queue, we unconditionally call
__veth_xdp_flush(rq). This guarantees that the NAPI consumer is scheduled,
making it solely responsible for re-waking the TXQ.
  This handles the race where veth_poll() consumes all packets and completes
NAPI *before* veth_xmit() on the producer side has called netif_tx_stop_queue.
The __veth_xdp_flush(rq) will observe rx_notify_masked is false and schedule
NAPI.

(2) On the consumer side, the logic for waking the peer TXQ is moved out of
veth_xdp_rcv() and placed at the end of the veth_poll() function. This
placement is part of fixing the race, as the netif_tx_queue_stopped() check
must occur after rx_notify_masked is potentially set to false during NAPI
completion.
  This handles the race where veth_poll() consumes all packets, but haven't
finished (rx_notify_masked is still true). The producer veth_xmit() stops the
TXQ and __veth_xdp_flush(rq) will observe rx_notify_masked is true, meaning
not starting NAPI.  Then veth_poll() change rx_notify_masked to false and
stops NAPI.  Before exiting veth_poll() will observe TXQ is stopped and wake
it up.

## Which versions are affected by CVE-2025-68232?


## How do I fix CVE-2025-68232?

Apply the vendor's patch.

## Is CVE-2025-68232 being exploited?

There is no known exploitation of CVE-2025-68232 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-68232 and fix it if it is affected.

What it is: CVE-2025-68232 is a high-severity vulnerability in Linux, published on 16 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-68232 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-2025-68232/ (Markdown: https://insights.sbomify.com/CVE-2025-68232/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-68232
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-68232
- OSV: https://osv.dev/vulnerability/CVE-2025-68232

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-68232/
Summaries are generated and may contain mistakes; the official description above is the record.