01 Record
CVE-2026-55040
Microsoft SharePoint Server Security Feature Bypass Vulnerability
CriticalKEVPUBLISHEDCNA: microsoft
CNA base score9.1 CVSS v3.xCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C
02 Description
Microsoft SharePoint Server Security Feature Bypass Vulnerability
03 Exploitation and scoring
- Exploitation
- Exploited in the wild. Listed in the CISA Known Exploited Vulnerabilities catalog on 2026-08-18. Federal remediation due 2026-08-21.
- SSVC decision
- ExploitationactiveCISA reports credible evidence of active exploitation.
- AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
- Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.
- EPSS probability
- 69.53% probability of exploitation activity in the next 30 days.
- EPSS percentile
- Equal to or higher than the score of 99.3% of scored records. A rank, not a probability.
- NVD base score
- 9.1 (CVSS v3.x), scored by the NVD independently of the CNA.
- NVD CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- NVD analysis status
- Analyzed. NVD last modified this record on 2026-08-19.
- Red Hat severity
- No Red Hat rating. Red Hat rates the CVEs that affect its products.
Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.
04 Metadata
- Published
- 2026-07-14 17:09Z3 MO AGO
- Last updated
- 2026-10-28 20:05Z20 HR AGO
- Reserved
- 2026-06-16
- Assigning CNA
- microsoft
- Record state
- PUBLISHED
- Severity
- Critical (CVSS 9.1)
- CNA CVSS vector
- 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
- Weaknesses
- CWE-1390Weak AuthenticationClass
- Data version
- 5.2
- Document digest
- a88ad2c3cc1a37982aa4a39198618b754dd64692a2949942863a5e0c91fe0106
05 Affected products
VendorProductVersionsPlatforms
MicrosoftMicrosoft SharePoint Server Subscription Edition16.0.0 to < 16.0.19725.20434x64-based Systems
06 References
- msrc.microsoft.comMicrosoft SharePoint Server Security Feature Bypass Vulnerabilityhttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040
- www.rapid7.comhttps://www.rapid7.com/blog/post/ra-microsoft-sharepoint-jwt-token-authentication-bypass-cve-2026-55040/
- github.comhttps://github.com/sfewer-r7/CVE-2026-55040
- www.cisa.govhttps://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-55040