Vulnerability details
CVE-2026-55040
Actively exploited
Microsoft SharePoint Enterprise ServerMicrosoft SharePoint Server
Microsoft SharePoint Server Security Feature Bypass Vulnerability
CVSS 3.1
9.1Critical
Official description
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
CVSS scores
| Score | Version | Source | Vector |
|---|---|---|---|
| 9.1Critical | 3.1 | CVEProject cvelistV5 (CNA) (microsoft) | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C |
Affected products
| Vendor | Product | Versions | Source |
|---|---|---|---|
| Microsoft | Microsoft SharePoint Enterprise Server 2016 | 16.0.0 ≤ v < 16.0.5561.1001 | CVEProject cvelistV5 (CNA) |
| Microsoft | Microsoft SharePoint Server 2019 | 16.0.0 ≤ v < 16.0.10417.20175 | CVEProject cvelistV5 (CNA) |
| Microsoft | Microsoft SharePoint Server Subscription Edition | 16.0.0 ≤ v < 16.0.19725.20434 | CVEProject cvelistV5 (CNA) |
References and advisories
4- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040 vendor-advisorypatch
- https://www.rapid7.com/blog/post/ra-microsoft-sharepoint-jwt-token-authentication-bypass-cve-2026-55040/ technical-description
- https://github.com/sfewer-r7/CVE-2026-55040 exploit
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-55040 government-resource
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Details
- Published
- 2026-07-14
- Last updated
- 2026-11-11
- State
- Published
- Assigner (CNA)
- microsoft
- Kolun priority
- 99 · Critical
CISA KEV catalog
- Date added
- 2026-08-18
- Due date
- 2026-08-21
- Used in ransomware
- Unknown
Exploit prediction (EPSS)
69.53%
Probability of exploitation in 30 days
99.3%
Percentile (among all CVEs)
SSVC assessment (CISA)
- Automatable
- Yes
- Exploitation
- Active
- Technical impact
- Total
Weaknesses (CWE)
- CWE-1390Weak Authentication