Microsoft SharePoint Server Deserialization of Untrusted Data Vulnerability
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.
Exploitation probability EPSS · FIRST
Exploitation signals 4 / 5
- KEV catalog (CISA)01 Jul 2026
- Exploited in EUVD (ENISA)01 Jul 2026
- Used by ransomwareyes
- EPSS above 10 %80.2%
- No account, over the networkno
What to do
Fix
Apply the vendor’s fix as soon as it is available.
CISA guidance: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
Meanwhile
Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.
Manufacturers (CRA)
Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained
Affected products
- 16.0.0 <16.0.10417.20128
- 16.0.0 <16.0.19725.20280
- 16.0.0 <16.0.5552.1002
Open source packages OSV
Affected libraries according to OSV, with fixed versions.
Timeline
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Published
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Exploitation reported (ENISA)
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Added to the KEV catalog
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CISA remediation due date
-
EPSS peak: 80.2%
References
Other exploited vulnerabilities from the same vendor
- CVE-2026-96951Microsoft Windows Command Injection Vulnerability5.6 · Actively exploited
- CVE-2026-65660Microsoft SharePoint Code Injection Vulnerability5.0 · Actively exploited
- CVE-2026-85880Microsoft Windows Heap-Based Buffer Overflow Vulnerability4.3 · Actively exploited
- CVE-2026-81963Microsoft Windows Link Following Vulnerability4.3 · Actively exploited
- CVE-2019-1068Microsoft SQL Server Remote Code Execution Vulnerability7.0 · Actively exploited
- CVE-2026-69836Microsoft Entra5.3 · Actively exploited