CVE-2026-55040: Microsoft Office SharePoint · Weak Authentication
Affects Microsoft SharePointSource GCVE Database
Exploited in the wild · KEV due 21 Aug 2026 · public detection template (Nuclei) · 69% EPSS · fixed in 16.0.5561.1001 : patch Microsoft SharePoint now.
Data as of 26 Oct 2026, 14:05 UTC
- KEV deadline
- US federal agencies must patch by this date; a sensible deadline for everyone else. Other KEV due dates
- EPSS
- 69.5% chance of exploitation in 30 days – higher than 99% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 16.0.5561.1001, 16.0.10417.20175, 16.0.19725.20434
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:CExploitation evidence
t = 0 is the CVE’s publication on cve.org
Disclosed: evidence found.
CVE published 14 Jul 2026
Detectable: evidence found.
nuclei template: Microsoft SharePoint Server - JWT Authentication Bypass
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: evidence found.
Listed in CISA KEV 35 days after disclosure
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
Timeline
CVE ID reserved
by Microsoft Corporation
, 28 days before disclosure
CVE published
on cve.org
, t = 0
In Threat Radar
record ingested
, 41 minutes after disclosure
Added to CISA KEV (opens in a new tab)
exploitation confirmed
, 35 days after disclosure
KEV remediation due
US federal deadline
, 38 days after disclosure
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA KEV (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade Microsoft SharePoint to 16.0.5561.1001 (Enterprise Server 2016) or 16.0.10417.20175 (Server 2019) or 16.0.19725.20434 (Server Subscription Edition).
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| MicrosoftMicrosoft SharePoint Enterprise Server 2016 | Affected
| Fixed in
|
| MicrosoftMicrosoft SharePoint Server 2019 | Affected
| Fixed in
|
| MicrosoftMicrosoft SharePoint Server Subscription Edition | Affected
| Fixed in
|
Description
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
References
- nvd.nist.gov/vuln/detail/CVE-2026-55040 (opens in a new tab)
- github.com/sfewer-r7/CVE-2026-55040 (opens in a new tab)
- msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040 (opens in a new tab)
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-55040 (opens in a new tab)
- rapid7.com/blog/post/ra-microsoft-sharepoint-jwt-token-authentication-bypass-cve-2026-55040 (opens in a new tab)