13 August 2026
Reference: CVE-2026-55040
1. What is being reported?
Researchers have discovered a critical vulnerability in Microsoft SharePoint’s authentication system. This weakness allows attackers to bypass security checks over the internet and potentially take control of the SharePoint system without needing to log in.
2. What this means in plain English
If exploited, attackers could access sensitive information or disrupt your SharePoint services without permission. This could lead to data loss, theft, or downtime, which can be costly and damaging for any organisation.
3. Could this affect a small business?
Small businesses and charities using Microsoft SharePoint are at risk, especially if their SharePoint is accessible over the internet. Organisations not using SharePoint or only using it internally with strong protections are less likely to be affected.
4. What to do now
- Contact your IT provider immediately to check if your SharePoint systems are vulnerable.
- Apply any available security updates or patches for Microsoft SharePoint as soon as possible.
- Review and strengthen your SharePoint access controls and network protections.
- Monitor your systems for unusual activity and report any suspicious behaviour.
5. Ask your IT provider
Can you confirm if our Microsoft SharePoint systems are affected by CVE-2026-55040 and have the necessary patches been applied to prevent authentication bypass?
6. Bottom line
Act quickly to update SharePoint and protect your organisation from this serious security risk.
Information based on CISA KEV, NVD, and reputable security news reports.