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NVD / CVE Program· CNA Linux

CVE-2025-21816: hrtimers: Force migrate away hrtimers queued after CPUHP_AP_HRTIMERS_DYING

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.20% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 2aecec58e9040ce3d2694707889f9914a2374955, 4.20, 5.11.

Low priority for now. Upgrade to Linux Linux 2aecec58e9040ce3d2694707889f9914a2374955, 4.20, 5.11 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: hrtimers: Force migrate away hrtimers queued after CPUHP_AP_HRTIMERS_DYING hrtimers are migrated away from the dying CPU to any online target at the CPUHP_AP_HRTIMERS_DYING stage in order not to delay bandwidth timers handling tasks involved in the CPU hotplug forward progress. However wakeups can still be performed by the outgoing CPU after CPUHP_AP_HRTIMERS_DYING. Those can result again in bandwidth timers being armed. Depending on several considerations (crystal ball power management based election, earliest timer already enqueued, timer migration enabled or not), the target may eventually be the current CPU even if offline. If that happens, the timer is eventually ignored. The most notable example is RCU which had to deal with each and every of those wake-ups by deferring them to an online CPU, along with related workarounds: _ e787644caf76 (rcu: Defer RCU kthreads wakeup when CPU is dying) _ 9139f93209d1 (rcu/nocb: Fix RT throttling hrtimer armed from offline CPU) _ f7345ccc62a4 (rcu/nocb: Fix rcuog wake-up from offline softirq) The problem isn't confined to RCU though as the stop machine kthread (which runs CPUHP_AP_HRTIMERS_DYING) reports its completion at the end of its work through cpu_stop_signal_done() and performs a wake up that eventually arms the deadline server timer: WARNING: CPU: 94 PID: 588 at kernel/time/hrtimer.c:1086 hrtimer_start_range_ns+0x289/0x2d0 CPU: 94 UID: 0 PID: 588 Comm: migration/94 Not tainted Stopper: multi_cpu_stop+0x0/0x120 <- stop_machine_cpuslocked+0x66/0xc0 RIP: 0010:hrtimer_start_range_ns+0x289/0x2d0 Call Trace: <TASK> start_dl_timer enqueue_dl_entity dl_server_start enqueue_task_fair enqueue_task ttwu_do_activate try_to_wake_up complete cpu_stopper_thread Instead of providing yet another bandaid to work around the situation, fix it in the hrtimers infrastructure instead: always migrate away a timer to an online target whenever it is enqueued from an offline CPU. This will also allow to revert all the above RCU disgraceful hacks.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Feb 27, 2025
Updated
Jun 17, 2026
EPSS
0.2% · 10th percentile
CWE
—

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel4.19.302 and later · before 4.20
  • linux linux kernel5.4.264 and later · before 5.5
  • linux linux kernel5.10.204 and later · before 5.11
  • linux linux kernel5.15.143 and later · before 5.16
  • linux linux kernel6.1.68 and later · before 6.1.141
  • linux linux kernel6.6.7 and later · before 6.6.93
  • linux linux kernel6.7.1 and later · before 6.12.14
  • linux linux kernel6.13 and later · before 6.13.3
  • linux linux kernel6.14
  • linux linux kernel6.7

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 9a2fc41acb69dd4e2a58d0c04346c3333c2341fc, 54d0d83a53508d687fd4a225f8aa1f18559562d0, 7f4c89400d2997939f6971c7981cc780a219e36b, 6fcbcc6c8e52650749692c7613cbe71bf601670d, 6.7affected
    • 75b5016ce325f1ef9c63e5398a1064cf8a7a7354 and later · before 82ac6adbbb2aad14548a71d5e2e37f4964a15e38affected · git
    • 53f408cad05bb987af860af22f4151e5a18e6ee8 and later · before 63815bef47ec25f5a125019ca480882481ee1553affected · git
    • 5c0930ccaad5a74d74e8b18b648c5eb21ed2fe94 and later · before e456a88bddae4030ba962447bb84be6669f2a0c1affected · git
    • 5c0930ccaad5a74d74e8b18b648c5eb21ed2fe94 and later · before 2aecec58e9040ce3d2694707889f9914a2374955affected · git
    • 5c0930ccaad5a74d74e8b18b648c5eb21ed2fe94 and later · before 53dac345395c0d2493cbc2f4c85fe38aef5b63f5affected · git
    • 6.1.68 and later · before 6.1.141affected · semver
    • 6.6.7 and later · before 6.6.93affected · semver
    • 4.19.302 and later · before 4.20affected · semver
    • 5.4.264 and later · before 5.5affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:11linux-6.1before 6.1.153-1~deb11u16.1.153-1~deb11u1
Debian:12linuxbefore 6.1.147-16.1.147-1
Debian:13linuxbefore 6.12.15-16.12.15-1
openSUSE:Leap 16.0dtb-aarch64before 6.12.0-160000.7.16.12.0-160000.7.1
openSUSE:Leap 16.0kernel-64kbbefore 6.12.0-160000.7.16.12.0-160000.7.1
openSUSE:Leap 16.0kernel-defaultbefore 6.12.0-160000.7.16.12.0-160000.7.1
openSUSE:Leap 16.0kernel-default-basebefore 6.12.0-160000.6.1.160000.2.46.12.0-160000.6.1.160000.2.4
openSUSE:Leap 16.0kernel-docsbefore 6.12.0-160000.7.16.12.0-160000.7.1
openSUSE:Leap 16.0kernel-kvmsmallbefore 6.12.0-160000.7.16.12.0-160000.7.1
openSUSE:Leap 16.0kernel-obs-buildbefore 6.12.0-160000.7.16.12.0-160000.7.1
openSUSE:Leap 16.0kernel-obs-qabefore 6.12.0-160000.7.16.12.0-160000.7.1
openSUSE:Leap 16.0kernel-rtbefore 6.12.0-160000.7.16.12.0-160000.7.1
openSUSE:Leap 16.0kernel-sourcebefore 6.12.0-160000.7.16.12.0-160000.7.1
openSUSE:Leap 16.0kernel-symsbefore 6.12.0-160000.7.16.12.0-160000.7.1
openSUSE:Leap 16.0kernel-zfcpdumpbefore 6.12.0-160000.7.16.12.0-160000.7.1
SUSE:Linux Enterprise Server 16.0kernel-docsbefore 6.12.0-160000.7.16.12.0-160000.7.1
SUSE:Linux Enterprise Server 16.0kernel-kvmsmallbefore 6.12.0-160000.7.16.12.0-160000.7.1
SUSE:Linux Enterprise Server 16.0kernel-obs-qabefore 6.12.0-160000.7.16.12.0-160000.7.1
SUSE:Linux Enterprise Server 16.0kernel-symsbefore 6.12.0-160000.7.16.12.0-160000.7.1
SUSE:Linux Enterprise Server 16.0kernel-zfcpdumpbefore 6.12.0-160000.7.16.12.0-160000.7.1
SUSE:Linux Micro 6.2kernel-64kbbefore 6.12.0-160000.7.16.12.0-160000.7.1
SUSE:Linux Micro 6.2kernel-defaultbefore 6.12.0-160000.7.16.12.0-160000.7.1
SUSE:Linux Micro 6.2kernel-default-basebefore 6.12.0-160000.6.1.160000.2.46.12.0-160000.6.1.160000.2.4
SUSE:Linux Micro 6.2kernel-rtbefore 6.12.0-160000.7.16.12.0-160000.7.1

+2

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe…KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2025-21813Feb 27, 2025 · timers/migration: Fix off-by-one root mis-connection
    22Monitor
  • ← EarlierCVE-2025-21815Feb 27, 2025 · mm/compaction: fix UBSAN shift-out-of-bounds warning
    28Monitor
  • Later →CVE-2025-21819Feb 27, 2025 · Revert "drm/amd/display: Use HW lock mgr for PSR1"
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux2aecec58e9040ce3d2694707889f9914a2374955Vendor (CNA)
Linux Linux4.20Vendor (CNA)
Linux Linux5.11Vendor (CNA)
Linux Linux5.16Vendor (CNA)
Linux Linux5.5Vendor (CNA)
Linux Linux53dac345395c0d2493cbc2f4c85fe38aef5b63f5Vendor (CNA)
Linux Linux6.1.141Vendor (CNA)
Linux Linux6.6.93Vendor (CNA)
Linux Linux63815bef47ec25f5a125019ca480882481ee1553Vendor (CNA)
Linux Linux82ac6adbbb2aad14548a71d5e2e37f4964a15e38Vendor (CNA)
Linux Linuxe456a88bddae4030ba962447bb84be6669f2a0c1Vendor (CNA)
cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0—Microsoft (MSRC)
debian:linux6.1.147-1 · Debian:12Package registry (OSV)
debian:linux-6.16.1.153-1~deb11u1 · Debian:11Package registry (OSV)
opensuse:dtb-aarch646.12.0-160000.7.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-64kb6.12.0-160000.7.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-default6.12.0-160000.7.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-default-base6.12.0-160000.6.1.160000.2.4 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-docs6.12.0-160000.7.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-kvmsmall6.12.0-160000.7.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-obs-build6.12.0-160000.7.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-obs-qa6.12.0-160000.7.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-rt6.12.0-160000.7.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-source6.12.0-160000.7.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-syms6.12.0-160000.7.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-zfcpdump6.12.0-160000.7.1 · openSUSE:Leap 16.0Package registry (OSV)
suse:kernel-64kb6.12.0-160000.7.1 · SUSE:Linux Micro 6.2Package registry (OSV)
suse:kernel-default6.12.0-160000.7.1 · SUSE:Linux Micro 6.2Package registry (OSV)
suse:kernel-default-base6.12.0-160000.6.1.160000.2.4 · SUSE:Linux Micro 6.2Package registry (OSV)
suse:kernel-docs6.12.0-160000.7.1 · SUSE:Linux Enterprise Server 16.0Package registry (OSV)

+7

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records