Kernel-level SMB client UAF affecting many Linux distributions and devices; can enable RCE/DoS on systems using CIFS/SMB — broad enterprise impact.
CVE-2026-89637
Linux kernel CIFS/SMB client UAF enabling potential RCE/DoS
Is CVE-2026-89637 being exploited?
Not confirmed. CVE-2026-89637 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 0.59% probability of exploitation in the next 30 days.
How severe is CVE-2026-89637?
CVE-2026-89637 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-2026-89637?
Yes. A fix has been recorded for CVE-2026-89637. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-89637 affect?
CVE-2026-89637 affects Linux kernel (CIFS/SMB client), Linux distributions using affected kernels, Servers mounting SMB shares, NAS/appliances using Linux kernel. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-89637?
Apply vendor/kernel security updates immediately; restrict/unmount untrusted SMB shares
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Use-after-free in CIFS SMB client allowing remote crash or potential remote code execution via malicious SMB server or MITM.
Immediate action required
- affected>= 316cf94a910f6f93d43cc574359d163ccae098a3 and < 9eed72e9534b10a6d9f8f5146feff3db53aebdba
- affected>= 316cf94a910f6f93d43cc574359d163ccae098a3 and < 5e6533a683f6a851158d9f33fb4ea8f4f25d7f84
- affected>= 316cf94a910f6f93d43cc574359d163ccae098a3 and < 730d0bb19507b9e19c2fe5343109ac618e2fbce5
- affected3.6
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.