CVE-2026-58644 Details.
Microsoft SharePoint Server - WS-Federation BinaryFormatter Deserialization RCE
Atlas does not check this one. Not a plain web check.
This weakness is not found through ordinary web pages. It needs a different kind of connection to the service. Atlas only runs plain web, DNS and TLS checks, so it does not run this one.
About CVE-2026-58644. What It Means.
Microsoft SharePoint Server (2016, 2019, Subscription Edition <= 2026.3.1) contains a remote code execution vulnerability in the WS-Federation passive sign-in endpoint (/_trust/default.aspx). The SharePoint authentication module (SPFederationAuthenticationModuleV2) uses a deflate-only DeflateCookieTransform (no MAC/signature check) to decode and BinaryFormatter to deserialize the SecurityContextToken Cookie value in the wresult parameter without type restrictions. An unauthe…
Affected Product. What Is Hit.
- Vendor
- microsoft
- Product
- Microsoft SharePoint Server
References. Where To Read More.
- https://nvd.nist.gov/vuln/detail/CVE-2026-58644
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-58644
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-58644
- https://github.com/WismanSec/sharepoint-2026-poc
- https://www.rapid7.com/blog/post/etr-cve-2026-58644-microsoft-sharepoint-server-unauthenticated-remote-code-execution-vulnerability-exploited-in-the-wild/
- https://documentation.n-able.com/N-central/Release_Notes/GA/Content/N-central_2026.3_HF1_Release_Notes.htm
More CVEs In Microsoft SharePoint Server.
FAQ
Common Questions.
Microsoft SharePoint Server - WS-Federation BinaryFormatter Deserialization RCE. Microsoft SharePoint Server (2016, 2019, Subscription Edition <= 2026.3.1) contains a remote code execution vulnerability in the WS-Federation passive sign-in endpoint (/_trust/default.aspx). The SharePoint authentication module (SPFederationAuthenticationModuleV2) uses a deflate-only DeflateCookieTransform (no MAC/signature check) to decode and BinaryFormatter to deserialize the SecurityContextToken Cookie value in the wresult parameter without type restrictions. An unauthe…
No. This weakness is not found through ordinary web pages. It needs a different kind of connection to the service. Atlas only runs plain web, DNS and TLS checks, so it does not run this one. The facts about CVE-2026-58644 are on this page, and you can request a demo to see how Brandefense watches your whole external attack surface.
Yes. CVE-2026-58644 is on the CISA Known Exploited Vulnerabilities list, which means attackers have used it against real targets.
Update Microsoft SharePoint Server to the latest version from the vendor, or follow the vendor's advice to switch off the affected feature. Vendor links are listed on this page when they are known.
This page lists the public facts about CVE-2026-58644. Atlas does not run a check for it, so nothing here says whether a particular site is affected.