How severe is CVE-2026-20963?

CVE-2026-20963 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-20963?

Affected package information for CVE-2026-20963 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2026-20963?

No fixed version has been published for CVE-2026-20963 yet. Monitor the advisory for updates, apply mitigations recommended by the vendor, and use O3 Security to track when a fix becomes available in your stack.

Is CVE-2026-20963 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-20963 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-20963?

CVE-2026-20963 has an EPSS (Exploit Prediction Scoring System) score of 5.3%, placing it in the 90th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

Is CVE-2026-20963 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2026-20963 (Microsoft SharePoint Deserialization of Untrusted Data Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2026-03-18. CISA required all US federal civilian agencies to remediate this vulnerability by 2026-03-21. The required action was: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2026-20963?

CVE-2026-20963 is classified as Deserialization of Untrusted Data (CWE-502). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

Which products and versions are affected by CVE-2026-20963?

CVE-2026-20963 affects microsoft sharepoint server (2 versions, e.g. 2016, 2019). Check the affected-products list on this page against your deployed version to confirm exposure.

When was CVE-2026-20963 published, and has it been updated?

CVE-2026-20963 was published on January 13, 2026 and was last updated on April 1, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2026-03-18 — agencies required to remediate by 2026-03-21

CVE-2026-20963

CRITICAL

Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.

Published

Jan 13, 2026

Updated

Apr 1, 2026

Affected

0 pkgs

Patched

None yet

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

5.3%probability of exploitation in next 30 days

Lower Risk90th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Description

Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.

Affected Products

1 product · 3 configurations

Application

sharepoint servermicrosoft

< 16.0.19127.20442

2 versions

20162019

Frequently Asked Questions

Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.

O3 Security · Impact-Aware SCA

Is CVE-2026-20963 in your stack?

O3 detects CVE-2026-20963 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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