CVE-2026-45659: Microsoft SharePoint Server Deserialization of Untrusted Data Vulnerability

Q: How do I fix CVE-2026-45659?

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

Q: Is CVE-2026-45659 being exploited?

Yes. CVE-2026-45659 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

Q: What does CVE-2026-45659 affect?

CVE-2026-45659 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-2026-45659?

Priority 91/100. High severity; EPSS top 1%: very likely to be exploited; Exploited in the wild (CISA KEV); Used in ransomware campaigns; On your watchlist

Patch now

HIGH 8.8EXPLOITEDWATCHLISTUPGRADE

CVE-2026-45659 is a high-severity flaw (CVSS 8.8) affecting sharepoint server, reported as exploited in the wild. 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
EPSS top 1%: very likely to be exploited
Exploited in the wild (CISA KEV)
Used in ransomware campaigns
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	80.2% (top 1%)
CISA exploited list	Yes, fix due 2026-07-04, used in ransomware
Weakness	CWE-502
Published	2026-05-22
Last modified	2026-07-23

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-07-23 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-22 23:16 UTCPublished CVE record published
2026-07-01Exploited Added to the CISA Known Exploited Vulnerabilities list
2026-07-04Deadline CISA due date for US federal agencies to patch
2026-07-23 11:10 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 ELN · clash-meta · FIXED · 1.19.33-1.eln159 · FEDORA-2026-7dfb64c5e1 · source

sudo dnf upgrade --advisory=FEDORA-2026-7dfb64c5e1

Fedora 46 · vulkan-utility-libraries · FIXED · 1.4.363.0-1.fc46 · FEDORA-2026-994176daf5 · source

sudo dnf upgrade --advisory=FEDORA-2026-994176daf5

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

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: HORKimhab/CVE-2026-45659 (1 stars)

Verify at the official source NVD · CVE Program · CISA KEV catalog · 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-2026-45659?

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

Is CVE-2026-45659 being exploited?

Yes. CVE-2026-45659 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

What does CVE-2026-45659 affect?

CVE-2026-45659 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-2026-45659?

Priority 91/100. High severity; EPSS top 1%: very likely to be exploited; Exploited in the wild (CISA KEV); Used in ransomware campaigns; 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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