CVE-2026-55040
Microsoft SharePoint Server Security Feature Bypass Vulnerability
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Microsoft SharePoint Server Security Feature Bypass Vulnerability
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
- Record
CVE-2026-55040- 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/E:U/RL:O/RC:C - Weakness
- CWE-1390
- Updated
- 2026-11-02
EUVDEUVD-2026-44211
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
- Record
EUVD-2026-44211- 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/E:U/RL:O/RC:C - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-grxw-7cvc-96rv
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a...
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
- Record
GHSA-grxw-7cvc-96rv- 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
- Updated
- 2026-11-02
CISA KEV No score
Microsoft SharePoint Weak Authentication Vulnerability
Microsoft SharePoint contains a weak authentication vulnerability which allows an unauthorized attacker to bypass a security feature over a network.
- Record
CVE-2026-55040- Weakness
- CWE-1390
- Updated
- 2026-11-02
NVD
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
- Record
CVE-2026-55040- 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
- Updated
- 2026-11-02
Affected products
Public exploits
Links only. Every CVE stores no exploit code.
| Source | Link | Date |
|---|---|---|
| PoC in GitHub | l0ggg/CVE-2026-55040 | 2026-07-28 |
| PoC in GitHub | sfewer-r7/CVE-2026-55040 | 2026-08-06 |
| PoC in GitHub | zenzue/CVE-2026-55040 | 2026-08-26 |
| PoC in GitHub | maxprog-svg/CVE-2026-55040-Mass-Exploit | 2026-08-27 |
| PoC in GitHub | virologi-info/mssharepoint-scanner | 2026-08-27 |
| Nuclei | Microsoft SharePoint Server - JWT Authentication Bypass |
History
| Recorded | Changed | Sources |
|---|---|---|
| exploitation, exploits | ||
| first indexed | CVE List, EUVD, GitHub Advisories, CISA KEV, Nuclei, NVD, PoC in GitHub |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-55040 is a critical vulnerability (CVSS 9.1) in Microsoft Sharepoint, published July 14, 2026. CISA lists it as known to be exploited, since August 18, 2026. EUVD reports exploitation since August 18, 2026. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 69.5%, the 99th percentile. No source names a fixed version.
References
msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040
rapid7.com/blog/post/ra-microsoft-sharepoint-jwt-token-authentication-bypass-cve-2026-55040
github.com/sfewer-r7/CVE-2026-55040
cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-55040
nvd.nist.gov/vuln/detail/CVE-2026-55040