Affects the Linux kernel Ceph client used broadly in servers/storage; can crash kernel on mount causing widespread outages across infrastructures.
CVE-2026-89651
Linux Ceph client: crafted MDS can trigger 4GiB OOB read causing kernel crash.
Is CVE-2026-89651 being exploited?
Not confirmed. CVE-2026-89651 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.63% probability of exploitation in the next 30 days.
How severe is CVE-2026-89651?
CVE-2026-89651 is rated Critical with a CVSS score of 9.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-89651?
Yes. A fix has been recorded for CVE-2026-89651. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-89651 affect?
CVE-2026-89651 affects Linux kernel (Ceph client), Systems mounting Ceph filesystems. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-89651?
Apply the patched Linux kernel with the Ceph decoder fix ASAP
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote malicious MDS can force the client kernel to perform up to a 4 GiB out‑of‑bounds read during session setup, causing crashes (DoS) and possible memory disclosure.
Immediate action required
- affected>= 1d17de9534cb5a4c4c380d174cc2f9281b34f89e and < dc5c7dffda92ef372fa587c444a1c537373df824
- affected>= 1d17de9534cb5a4c4c380d174cc2f9281b34f89e and < c37db86d2b5e9b57001ccae7e7a727e95a4f9c02
- affected>= 1d17de9534cb5a4c4c380d174cc2f9281b34f89e and < 5f892c767b30e4fb0c744c59f9235c717383d2cd
- affected>= 1d17de9534cb5a4c4c380d174cc2f9281b34f89e and < 77933e22adfe813be2bd10be08d6e950103c3967
- affected6.10
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.