CVE-2025-21771: Linux kernel · sched_ext: Fix incorrect autogroup migration detection
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium.
Data as of 29 Oct 2026, 23:28 UTC
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 27 Feb 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 24.04 LTSlinux-raspi-realtimepkg:deb/ubuntu/linux-raspi-realtime?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSlinux-allwinner-5.19pkg:deb/ubuntu/linux-allwinner-5.19?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSlinux-aws-5.19pkg:deb/ubuntu/linux-aws-5.19?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSlinux-aws-6.2pkg:deb/ubuntu/linux-aws-6.2?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSlinux-aws-6.5pkg:deb/ubuntu/linux-aws-6.5?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSlinux-azure-5.19pkg:deb/ubuntu/linux-azure-5.19?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A fix is available that modifies sched_move_task() to explicitly indicate the migration type and restricts scx_move_task() usage to cgroup migrations only. Users should apply the updated Linux kernel versions that include this patch to resolve the issue.
Description
CVE-2025-21771 addresses a flaw in the Linux kernel's scheduler extension where the function scx_move_task() incorrectly detects autogroup migrations. This caused the function to ignore certain migrations improperly, leading to kernel warnings. The issue was fixed by modifying sched_move_task() to explicitly indicate the type of migration, ensuring scx_move_task() is only called for cgroup migrations.
References
- ubuntu.com/security/CVE-2025-21771 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-21771 (opens in a new tab)
- git.kernel.org/linus/d6f3e7d564b2309e1f17e709a70eca78d7ca2bb8 (opens in a new tab)
- git.kernel.org/stable/c/75bf2f80c046d2ec5a07455891ea0a9fb6d8b5f6 (opens in a new tab)
- git.kernel.org/stable/c/d6f3e7d564b2309e1f17e709a70eca78d7ca2bb8 (opens in a new tab)
- git.kernel.org/stable/c/d8b510d0ddc65d8a71e0f9a3acc9ed5f010fc514 (opens in a new tab)