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VulnerabilityPublished Updated

CVE-2026-55040: Microsoft Office SharePoint · Weak Authentication

Affects Microsoft SharePointSource GCVE Database

0
Authoritative record:CVE-2026-55040· Critical 9.1

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

CVSS 3.1 base score
9.1Critical
How severe the flaw is on the 0–10 CVSS scale.
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:C

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

  1. Disclosed: evidence found.

    CVE published 14 Jul 2026

  2. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  3. Exploited in the wild: evidence found.

    Listed in CISA KEV 35 days after disclosure

  4. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

Timeline

  1. CVE ID reserved

    by Microsoft Corporation

    , 28 days before disclosure

  2. CVE published

    on cve.org

    , t = 0

  3. In Threat Radar

    record ingested

    , 41 minutes after disclosure

  4. , 35 days after disclosure

  5. 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

ProductAffectedFixed in
MicrosoftMicrosoft SharePoint Enterprise Server 2016Affected
  • >=16.0.0 <16.0.5561.1001
Fixed in
  • 16.0.5561.1001
MicrosoftMicrosoft SharePoint Server 2019Affected
  • >=16.0.0 <16.0.10417.20175
Fixed in
  • 16.0.10417.20175
MicrosoftMicrosoft SharePoint Server Subscription EditionAffected
  • >=16.0.0 <16.0.19725.20434
Fixed in
  • 16.0.19725.20434

Description

Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.

References

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