Vulnerability
CVE-2026-55040
Microsoft SharePoint Server: unauthenticated security feature bypass
Most severe levelDEFCON 3 · Substantial risk
Official data
- CVSS 3.1
- 9.1 · critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N - Weakness
- CWE-1390
- EPSS
- 69.54% probability of exploitation in the next 30 days, higher than 99% of CVEs
- CISA KEV catalogue
- Yes, since 18 August 2026
Sources: NVD (CVSS, weakness, publication), FIRST (EPSS), CISA (KEV catalogue).
Data read on 25 October 2026.
Timeline
- 14 July 2026Published on NVD
- 14 July 2026First in the DefenceLevel briefing
- 18 August 2026Added to the CISA KEV catalogue
In DefenceLevel briefings5 days
- 21 August 2026Still ongoingDEFCON 4
- 20 August 2026Still ongoingDEFCON 4
- 19 August 2026New in the last 24 hoursDEFCON 3
- 15 July 2026New in the last 24 hoursDEFCON 3
- 14 July 2026New in the last 24 hoursDEFCON 4
Last 12 months.
The full analysis is in the briefingThe full analysis is in your archive
Why it matters now, who is affected and what to do: every day at 05:00 UTC, for subscribers.Why it matters, who is affected and what to do, as in the daily briefing.
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