VULNOS
All Threat Alerts
criticalCVE Alert
CVE-2026-89655

Critical Vulnerability: CVE-2026-89655

In the Linux kernel, the following vulnerability has been resolved: ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock list_for_each_entry() iterates ci->i_cap_flush_list but drops i_ceph_lock to send cap messages. During the unlock window, handle_cap_flush_ack() can acquire i_ceph_lock, detach cf entries with tid <= flush_tid from the list, release i_ceph_lock, and free them via ceph_free_cap_flush() outside any lock. When the original thread reacquires i_ceph_lock and

Monday, September 14, 2026Vulnios Threat Intelligence
Share:

Vulnerability Snapshot

CVE-2026-89655 is rated CRITICAL — exploitation is trivial or already observed in the wild and impact is severe. Patch immediately, not on the next maintenance window.

Executive Summary

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

ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock

list_for_each_entry() iterates ci->i_cap_flush_list but drops

i_ceph_lock to send cap messages. During the unlock window,

handle_cap_flush_ack() can acquire i_ceph_lock, detach cf entries

with tid <= flush_tid from the list, release i_ceph_lock, and free

them via ceph_free_cap_flush() outside any lock. When the original

thread reacquires i_ceph_lock and the for-loop macro advances via

cf = list_next_entry(cf, i_list), it dereferences cf->i_list.next

on freed memory.

The race timeline:

__kick_flushing_caps() handle_cap_flush_ack()

----------------------- -----------------------

holds i_ceph_lock <---

iterates to cf (tid=10)

prepares FLUSH message

drops i_ceph_lock <---

__send_cap() ── FLUSH(tid=10)

MDS sends FLUSH_ACK(tid=10)

--->

Why It Matters

CVE-2026-89655 is rated CRITICAL severity, requiring immediate attention from security teams.

CVSS Base Score: 9.8/10

🛡️What Defenders Should Check

  • Check if you are affected — Review your asset inventory for products listed in CVE-2026-89655.
  • Apply available patches — Visit vendor advisories for the latest security updates.
  • Monitor for exploitation — Check your SIEM/IDS logs for related indicators.

    • Use Vulnios to continuously monitor your exposure to CVE-2026-89655 and similar vulnerabilities.

    References & Sources

  • https://git.kernel.org/stable/c/01542430081014d80fc9e70e92d6647432ddb7fc
  • https://git.kernel.org/stable/c/091137821e1fc88f37e15201abf055c9494ddc61
  • https://git.kernel.org/stable/c/19f16f04c2b014a7dd214dc1e42557d8530b16f3
  • https://git.kernel.org/stable/c/23eb34a53a53cb1a6dab1eeee830633207ac158d
  • https://git.kernel.org/stable/c/2701431aa3cc8b23efe6890182e7b04f5e76fab5
  • https://git.kernel.org/stable/c/2dba24dcd5050be4b7b119e6f0b01f62203b5d26
  • https://git.kernel.org/stable/c/7af4c4f01305b0935adf6d4301b1ec407025485d
  • https://git.kernel.org/stable/c/fe46746087b5b9c5bb2d022df6c7819218494ced

    • How Vulnios Detects This

    Vulnios scans for this vulnerability using Trivy and Grype for SBOM-based CVE matching and Vulnios CVE feed continuous monitoring against your asset inventory. Run a scan against your environment to see whether you are exposed; findings are linked back to the original CVE record so triage starts with the patch path already known.

    AI Security Advisor

    Powered by Gemini

    Get AI-powered security recommendations tailored to this specific threat — including risk assessment, detection guidance, MITRE ATT&CK mapping, and actionable remediation steps.

    Sources

    Related Threat Alerts

    Frequently Asked Questions

    What is CVE-2026-89655?

    CVE-2026-89655 is a critical-severity vulnerability tracked under the Common Vulnerabilities and Exposures program. In the Linux kernel, the following vulnerability has been resolved:

    ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock

    list_for_each_entry() iterates ci->i_cap_flush_list but dr

    Am I affected?

    Affected technology is listed in the Affected Products section above. If your asset inventory contains any of them, assume in-scope until you can prove otherwise.

    How urgent is the response?

    Critical: do not wait for your normal patch cycle. Verify exposure today, apply the vendor patch immediately, and add detection rules for any post-exploit indicators.

    How do I remediate?

    Apply the vendor patch listed in the upstream advisory linked under Sources. If the patch is not yet available, follow the vendor-supplied workaround (often a config flag or feature disable) and add detections for the published exploit pattern in your SIEM. Re-scan after the patch lands to confirm the finding clears.

    Where can I track exploitation activity?

    Watch CISA's Known Exploited Vulnerabilities catalog for CVE-2026-89655. Cross-reference with public exploit databases and your own SIEM/IDS for indicator-of-compromise patterns. Vulnios tracks KEV status automatically and surfaces it on the asset findings view.

    How does Vulnios help with this?

    Vulnios continuously cross-references your asset inventory against the live CVE feed (NVD, vendor advisories, CISA KEV, and curated OSINT). When a new CVE matches your environment, you get a prioritized finding with the severity, KEV status, exploit-prediction (EPSS), and a direct path to the vendor patch. You can start a free scan from the homepage.

    critical

    Protect Your Organization

    Monitor CVEs, scan for vulnerabilities, and get real-time threat alerts — all in one platform.

    Get Started FreeFree Security ScanOSINT Dashboard

    Weekly threat digest

    KEV-listed exploits and vendor advisories, every Monday.

    One email a week. Unsubscribe any time.

    Get instant alerts on Telegram

    Join our public channel for real-time critical CVE alerts.

    Follow @vulnios