critical Known exploitedREV. 01
CVE-2026-55040SharePoint — Weak Authentication Bypasses a Security Feature
Microsoft SharePoint's authentication is weak enough that an attacker with only network access can bypass a security check without any credentials, and go on to read and change data on the server.
Read the risk
THE VITAL STATS- CVSS score
- 9.1/ 10 CVSS v3.1
- EPSS probability
- 51% Likelihood of exploitation
- Attack complexity
- Low Conditions needed to exploit
- Known exploited
- Yes — CISA KEV
- CVE published
- 2026-07-14
- Added to KEV
- 2026-08-18
- Exploit published
- Yes
- Confidence
- medium
- Kill chain
- initial access
- MITRE ATT&CK
- T1190, T1078
- Severity
- critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Attacker needsNetwork access to the SharePoint server
Behind the card
5 REFERENCES- 01CVE recordNVD recordnvd.nist.gov
- 02CISACISA Known Exploited Vulnerabilities catalogcisa.gov
- 03Vendor advisorymsrc.microsoft.commsrc.microsoft.com
- 04Exploitgithub.comgithub.com
- 05Exploitcisa.govcisa.gov
Field-level provenanceTRACE THE SOURCES +
Which source supports each field, when it was retrieved, and who extracted it.
| Fields | Source | Retrieved | Extractor | Confidence |
|---|---|---|---|---|
| cvss, exploitation.attack_complexity, exploitation.exploit_available, references, published_at | nvd.nist.gov | 2026-09-21 | scrty-crds-pipeline/0.1 | high |
| exploitation.known_exploited, exploitation.kev_added | cisa.gov | 2026-09-21 | scrty-crds-pipeline/0.1 | high |
| epss | api.first.org | 2026-09-21 | scrty-crds-pipeline/0.1 | high |
| title, summary, severity, remediation, mitre_attack, kill_chain, recommended_action, confidence, tags, exploitation.prerequisites | nvd.nist.gov | 2026-09-21 | claude-code | high |
Printing history
THE RECORD- r1Initial base card
First printing. This card has not been reprinted since publication.