CVE-2026-40357: Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code

Q: How do I fix CVE-2026-40357?

sharepoint server: upgrade to 16.0.19725.20280. Exact commands for each OS are on this page.

Q: Is CVE-2026-40357 being exploited?

CVE-2026-40357 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-40357 affect?

CVE-2026-40357 affects sharepoint server. Severity is high (CVSS 8.8). Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.

Q: How urgent is CVE-2026-40357?

Priority 55/100. High severity; On your watchlist

This month

HIGH 8.8WATCHLISTUPGRADE

CVE-2026-40357 is a high-severity flaw (CVSS 8.8) affecting sharepoint server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	1.7% (top 23%)
CISA exploited list	No
Weakness	CWE-502
Published	2026-05-12
Last modified	2026-10-26

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-12 18:17 UTCPublished CVE record published
2026-10-26 18:10 UTCUpdated Record last modified

microsoft sharepoint server UPGRADE

Affected: < 16.0.19725.20280 · 2016 · 2019

Fixed in: 16.0.19725.20280

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy sharepoint-server || rpm -q sharepoint-server || sharepoint-server --version

2. UPGRADE to 16.0.19725.20280 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade sharepoint-server

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade sharepoint-server

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Exact fixes by distribution

Fedora 46 · ddnet · FIXED · 20.2-1.fc46 · FEDORA-2026-6991b4ab14 · source

sudo dnf upgrade --advisory=FEDORA-2026-6991b4ab14

Fedora ELN · libplacebo · FIXED · 7.360.1-5.eln159 · FEDORA-2026-92226f221e · source

sudo dnf upgrade --advisory=FEDORA-2026-92226f221e

Microsoft SharePoint Enterprise Server 2016 · KB5002868 · FIXED · 16.0.5552.1002 · KB5002868 · source

Install KB5002868 via Windows Update, then verify: Get-HotFix -Id KB5002868

Microsoft SharePoint Server 2019 · KB5002870 · FIXED · 16.0.10417.20128 · KB5002870 · source

Install KB5002870 via Windows Update, then verify: Get-HotFix -Id KB5002870

Microsoft SharePoint Server Subscription Edition · KB5002863 · FIXED · 16.0.19725.20280 · KB5002863 · source

Install KB5002863 via Windows Update, then verify: Get-HotFix -Id KB5002863

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-40357?

sharepoint server: upgrade to 16.0.19725.20280. Exact commands for each OS are on this page.

Is CVE-2026-40357 being exploited?

CVE-2026-40357 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-40357 affect?

CVE-2026-40357 affects sharepoint server. Severity is high (CVSS 8.8). Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.

How urgent is CVE-2026-40357?

Priority 55/100. High severity; On your watchlist

Software pages

SharePoint vulnerabilities · Microsoft Office vulnerabilities

Related CVEs

CVE-2026-32201 MEDIUM 6.5 EXPLOITED UPGRADE Microsoft SharePoint Server Improper Input Validation Vulnerability
CVE-2026-20945 MEDIUM 4.6 UPGRADE Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Office Share
CVE-2026-33112 HIGH 8.8 UPGRADE Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code
CVE-2026-33110 HIGH 8.8 UPGRADE Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code
CVE-2026-35439 HIGH 8.8 UPGRADE Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code

References

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