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CVE-2026-89650

Critical Vulnerability: CVE-2026-89650

In the Linux kernel, the following vulnerability has been resolved: ceph: bound num_export_targets array for mds info v2/v3 ceph_mdsmap_decode() in fs/ceph/mdsmap.c reads num_export_targets from each per-mds info record and advances the decode cursor by num_export_targets * sizeof(u32) without first checking that many bytes remain. The only upper-bound check that catches a runaway cursor (*p > info_end) is gated on info_v >= 4, because info_end is left NULL for info_v 2 and 3. When the monitor

Monday, September 14, 2026Vulnios Threat Intelligence
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Vulnerability Snapshot

CVE-2026-89650 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: bound num_export_targets array for mds info v2/v3

ceph_mdsmap_decode() in fs/ceph/mdsmap.c reads num_export_targets from

each per-mds info record and advances the decode cursor by

num_export_targets * sizeof(u32) without first checking that many bytes

remain. The only upper-bound check that catches a runaway cursor

(*p > info_end) is gated on info_v >= 4, because info_end is left NULL

for info_v 2 and 3. When the monitor sends an MDS map whose per-mds

info version is 2 or 3 with an oversized num_export_targets, the cursor

moves past the message front buffer and the later export-targets loop

calls the unchecked ceph_decode_32() on out-of-bounds memory.

A kernel client processes CEPH_MSG_MDS_MAP from its monitor session

(net/ceph/mon_client.c dispatches it; fs/ceph/super.c routes it to

ceph_mdsc_handle_mdsmap(), which sets end to the front buffer bound and

calls ceph_mdsmap_decode()). A malicious or compromised

Why It Matters

CVE-2026-89650 is rated CRITICAL severity, requiring immediate attention from security teams.

CVSS Base Score: 9.1/10

🛡️What Defenders Should Check

  • Check if you are affected — Review your asset inventory for products listed in CVE-2026-89650.
  • 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-2026-89650 and similar vulnerabilities.

    References & Sources

  • https://git.kernel.org/stable/c/0c4bcc3ba7291d383b82ce1c2fe324f69a42da2d
  • https://git.kernel.org/stable/c/332c444f4dc6fa1e8b8637c9e82d29e97f768656
  • https://git.kernel.org/stable/c/3bf7dba8dba9a05774b846affec61a3624ddba38
  • https://git.kernel.org/stable/c/55a06b32438c222765138727d0a8164b103e8f0d
  • https://git.kernel.org/stable/c/58c2d3e954c13694ef6e820a5e9456461bb9e7df
  • https://git.kernel.org/stable/c/a3eb169ee297aa99670ba927c659990bd1e453f3
  • https://git.kernel.org/stable/c/eb3e1a1cb1634c76d59c5a9cb1a026fc69d40911

    • 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.

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    Sources

    Related Threat Alerts

    Frequently Asked Questions

    What is CVE-2026-89650?

    CVE-2026-89650 is a critical-severity vulnerability tracked under the Common Vulnerabilities and Exposures program. In the Linux kernel, the following vulnerability has been resolved:

    ceph: bound num_export_targets array for mds info v2/v3

    ceph_mdsmap_decode() in fs/ceph/mdsmap.c reads num_export_targets from

    eac

    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-2026-89650. 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.

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