Vulnerability · CVE-2026-66805
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
Published Aug 11, 2026 · catalog updated Oct 21, 2026 · sharepoint server
Last checked Oct 26, 2026. A connected source was read within the last 7 days.
Check if you run it
No confirmed exploitation is on record for CVE-2026-66805. EPSS is 2.04%. Act only if a listed version of sharepoint server is installed.
Gaps on this record
- No vendor fix or required action is stored. Compare the linked advisory before you change production.
Same product and reporting
- CVE-2026-70259 · Medium
- CVE-2026-69943 · High
- CVE-2026-102859 · Medium
- CVE-2026-63520 · High · known exploited
- CVE-2026-55040 · Critical · known exploited
- Severity
- High8.8
- Known exploitation
- Not in CISA/VulnCheck KEV
- EPSS
- 2.04%
- Remediation
- Version ranges on file
- Affected products
- cpe microsoft/sharepoint server
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
Are you affected?
Enter the version you run. The result uses only the ranges stored on this record.
The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.
- cpe microsoft/sharepoint server2016
- cpe microsoft/sharepoint server2019
- cpe microsoft/sharepoint server< 16.0.19725.20522
How to fix CVE-2026-66805
Upgrade
CVE-2026-66805 lists a fix boundary at 16.0.19725.20522. Compare the installed build with that boundary before you change production.
Version check
Affected < 16.0.19725.20522
Advisory
Open the cve_org record and follow its fix.
Official advisories
What to do
Three questions, each answered from this record only. Confirm the vendor advisory before you patch.
Should you patch?
No confirmed exploitation is on record for CVE-2026-66805. EPSS is 2.04%. Act only if a listed version of sharepoint server is installed.
Which versions are affected?
Compare what you have installed with microsoft/sharepoint server 2016; microsoft/sharepoint server 2019; microsoft/sharepoint server < 16.0.19725.20522. Compare the installed version with the linked vendor advisory before you change production.
What should an analyst verify?
CWE-502: Deserialization of Untrusted Data. EPSS 2.04%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Aug 11, 2026 · NIST NVD
Detected
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
Oct 21, 2026 · NIST NVD
Updated
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
Sources
- CVE.orgVulnerability recordCVE-2026-66805
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2026-66805
30-day exploitation probability 2.04%
first.org - NIST NVDVulnerability recordCVE-2026-66805
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
nvd.nist.gov
References
Freshness
Last verified in this catalog Oct 26, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.
- FIRST EPSSOct 23, 2026
- CVE.orgOct 22, 2026
- NIST NVDOct 22, 2026