# CVE-2026-23371: sched/deadline: Fix missing ENQUEUE_REPLENISH during PI de-boosting

> A logic error in the Linux kernel's deadline scheduler can cause bandwidth accounting corruption and system warnings, potentially leading to denial of service.

- **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 Mar 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-80663, BELL-CVE-2026-23371, DEBIAN-CVE-2026-23371, GHSA-55fv-ccjv-2hr3, ROOT-OS-DEBIAN-11-CVE-2026-23371, ROOT-OS-DEBIAN-12-CVE-2026-23371, ROOT-OS-DEBIAN-13-CVE-2026-23371, ROOT-OS-UBUNTU-2204-CVE-2026-23371, ROOT-OS-UBUNTU-2404-CVE-2026-23371, UBUNTU-CVE-2026-23371

## What is CVE-2026-23371?

CVE-2026-23371 is a medium-severity denial of service vulnerability in Linux kernel, published on 25 Mar 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:

sched/deadline: Fix missing ENQUEUE_REPLENISH during PI de-boosting

Running stress-ng --schedpolicy 0 on an RT kernel on a big machine
might lead to the following WARNINGs (edited).

 sched: DL de-boosted task PID 22725: REPLENISH flag missing

 WARNING: CPU: 93 PID: 0 at kernel/sched/deadline.c:239 dequeue_task_dl+0x15c/0x1f8
 ... (running_bw underflow)
 Call trace:
  dequeue_task_dl+0x15c/0x1f8 (P)
  dequeue_task+0x80/0x168
  deactivate_task+0x24/0x50
  push_dl_task+0x264/0x2e0
  dl_task_timer+0x1b0/0x228
  __hrtimer_run_queues+0x188/0x378
  hrtimer_interrupt+0xfc/0x260
  ...

The problem is that when a SCHED_DEADLINE task (lock holder) is
changed to a lower priority class via sched_setscheduler(), it may
fail to properly inherit the parameters of potential DEADLINE donors
if it didn't already inherit them in the past (shorter deadline than
donor's at that time). This might lead to bandwidth accounting
corruption, as enqueue_task_dl() won't recognize the lock holder as
boosted.

The scenario occurs when:
1. A DEADLINE task (donor) blocks on a PI mutex held by another
   DEADLINE task (holder), but the holder doesn't inherit parameters
   (e.g., it already has a shorter deadline)
2. sched_setscheduler() changes the holder from DEADLINE to a lower
   class while still holding the mutex
3. The holder should now inherit DEADLINE parameters from the donor
   and be enqueued with ENQUEUE_REPLENISH, but this doesn't happen

Fix the issue by introducing __setscheduler_dl_pi(), which detects when
a DEADLINE (proper or boosted) task gets setscheduled to a lower
priority class. In case, the function makes the task inherit DEADLINE
parameters of the donoer (pi_se) and sets ENQUEUE_REPLENISH flag to
ensure proper bandwidth accounting during the next enqueue operation.

## Which versions are affected by CVE-2026-23371?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23371?

Apply the vendor's patch.

## Is CVE-2026-23371 being exploited?

There is no known exploitation of CVE-2026-23371 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-2026-23371 and fix it if it is affected.

What it is: CVE-2026-23371 is a medium-severity denial of service vulnerability in Linux kernel, published on 25 Mar 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-2026-23371 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-2026-23371/ (Markdown: https://insights.sbomify.com/CVE-2026-23371/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23371
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23371
- OSV: https://osv.dev/vulnerability/CVE-2026-23371

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23371/
Summaries are generated and may contain mistakes; the official description above is the record.