How severe is CVE-2026-89647?

CVE-2026-89647 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-89647?

CVE-2026-89647 affects the following packages: Kernel (Linux). Ecosystems affected: Linux.

How do I fix CVE-2026-89647?

Update Kernel to 6.12.109 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-89647 is resolved across your whole dependency graph.

How do I detect CVE-2026-89647 in my Linux dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Kernel. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2026-89647 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-89647?

O3 pinpoints whether CVE-2026-89647 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2026-89647 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-89647 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was CVE-2026-89647 published, and has it been updated?

CVE-2026-89647 was published on September 11, 2026 and was last updated on September 14, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐧

🐧 Linux

Not in CISA KEV

HIGH severity

CVE-2026-89647

HIGH

CVE-2026-89647 is a high-severity (CVSS 7.5) vulnerability in Kernel. O3 Security confirms whether CVE-2026-89647 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

ceph: do not repeat ceph_trim_dentries() if no progress possible

Published

Sep 11, 2026

Updated

Sep 14, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 14, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

🐧Kernel

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Linux packages — download data is not available via public APIs for these ecosystems.

Description

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

ceph: do not repeat ceph_trim_dentries() if no progress possible

ceph_cap_reclaim_work() re-queues itself for as long as ceph_trim_dentries() returns -EAGAIN, which happens whenever a lease walk exhausts its nr_to_scan budget. This creates a busy loop that consumes CPU without making any progress when there is nothing to reclaim: with no cap pressure (count==0) and every scanned lease still valid, each pass runs the full scan budget down to zero and returns -EAGAIN, only to be queued again immediately.

The dir-lease walk made this worse. When expire_dir_lease is false (i.e. we have no intention of reclaiming dir leases), __dir_lease_check() returned TOUCH for every valid lease. TOUCH moves the dentry to the tail of the list and resets di->time via __dentry_dir_lease_touch(), so a walk over N valid leases pointlessly rewrote the list, refreshed the timestamps (preventing them from ever aging out) and always drained nr_to_scan, guaranteeing the -EAGAIN requeue.

Fix this in three steps:

Return KEEP instead of TOUCH when expire_dir_lease is false. If we are not going to reclaim the lease, leave it in place instead of churning the list and resetting its timestamp; the walk then terminates naturally (or via STOP at the first fresh lease).
Only return -EAGAIN from the first (dentry-lease) walk when something was actually freed. A full batch that frees nothing means retrying the same list immediately is futile; fall through to the dir-lease walk instead.
After both walks, bail out with success (0) when nothing was freed and there is no cap pressure (count==0). There is no reason to keep retrying when we are not over the cap limit and made no progress.

Under real cap pressure (count>0) the reclaim path is unchanged and still retries via -EAGAIN.

Without this patch, I saw 500 ceph_trim_dentries() calls per second on our web servers. This is very visible in /proc/lock_stat (5 minute capture):

          class name    con-bounces    contentions   waittime-min   waittime-max waittime-total   waittime-avg    acq-bounces   acquisitions   holdtime-min   holdtime-max holdtime-total   holdtime-avg

&mdsc->dentry_list_lock: 126180 128218 0.04 8063.44 15986965.20 124.69 1573354 5296812 0.04 8291.28 74164526.48 14.00

&mdsc->dentry_list_lock 111736 [<000000007b11e319>] __ceph_dentry_dir_lease_touch+0x7c/0xa8 &mdsc->dentry_list_lock 2631 [<0000000050597999>] __dentry_leases_walk+0x64/0x2c8 &mdsc->dentry_list_lock 3878 [<00000000c0022f62>] __ceph_dentry_lease_touch+0x5c/0xa8 &mdsc->dentry_list_lock 9973 [<000000002f27cb6f>] __dentry_lease_unlist+0x50/0xa0

&mdsc->dentry_list_lock 123621 [<0000000050597999>] __dentry_leases_walk+0x64/0x2c8 &mdsc->dentry_list_lock 1822 [<000000007b11e319>] __ceph_dentry_dir_lease_touch+0x7c/0xa8 &mdsc->dentry_list_lock 2720 [<000000002f27cb6f>] __dentry_lease_unlist+0x50/0xa0 &mdsc->dentry_list_lock 55 [<00000000c0022f62>] __ceph_dentry_lease_touch+0x5c/0xa8

With this patch:

          class name    con-bounces    contentions   waittime-min   waittime-max waittime-total   waittime-avg    acq-bounces   acquisitions   holdtime-min   holdtime-max holdtime-total   holdtime-avg

&mdsc->dentry_list_lock: 1203 1215 0.16 408.88 33082.88 27.23 4320501 7357389 0.04 500.64 1961578.00 0.27

&mdsc->dentry_list_lock 1029 [<000000003c9aea8a>] __ceph_dentry_dir_lease_touch+0x7c/0xa8 &mdsc->dentry_list_lock 1 ---truncated---

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐧Linux	`Kernel`	≥ 5.1.0&&< 6.12.109	6.12.109

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Kernel. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update Kernel to 6.12.109 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-89647 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-89647 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2026-89647. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

In the Linux kernel, the following vulnerability has been resolved: ceph: do not repeat ceph_trim_dentries() if no progress possible ceph_cap_reclaim_work() re-queues itself for as long as ceph_trim_dentries() returns -EAGAIN, which happens whenever a lease walk exhausts its `nr_to_scan` budget. This creates a busy loop that consumes CPU without making any progress when there is nothing to reclaim: with no cap pressure (`count==0`) and every scanned lease still valid, each pass runs the full scan budget down to zero and returns `-EAGAIN`, only to be queued again immediately. The dir-lease

O3 Security · Impact-Aware SCA

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