Authenticated remote code execution in widely deployed Microsoft SharePoint; high-impact enterprise product requiring org-wide attention.
CVE-2026-123390
Authenticated deserialization RCE in Microsoft SharePoint
Is CVE-2026-123390 being exploited?
Not confirmed. CVE-2026-123390 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 1.7% probability of exploitation in the next 30 days.
How severe is CVE-2026-123390?
CVE-2026-123390 is rated High with a CVSS score of 8.8. 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-2026-123390?
Yes. A fix has been recorded for CVE-2026-123390. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-123390 affect?
CVE-2026-123390 affects Microsoft SharePoint Server (on-premises), Microsoft SharePoint deployments. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-123390?
Apply Microsoft security updates immediately; restrict SharePoint access and monitor logs.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated remote code execution via deserialization; attacker with SharePoint access can execute arbitrary code on the server.
Immediate action required
- affected>= 16.0.0 and < 16.0.20326.20136
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.
cisa ssvc
- exploitation
- none
- automatable
- no
- technical impact
- total
Assessed by CISA 10 Nov 2026 (SSVC 2.0.3).
timeline
- 10 Nov 2026Published
- 10 Nov 2026CISA SSVC assessment: exploitation none · same day later
- 10 Nov 2026CVE record last updated · same day later
- 11 Nov 2026Analysed by vulneraibility.com · same day later
- Patchmsrc.microsoft.com /update-guide/vulnerability/CVE-2026-123390
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.