Patch tracker / KB5002835
KB5002835: Office Online Server Security Update (February 2026)
KB5002835 is a High security update for Office Online Server, released 2026-02-10. It closes 3 CVEs with a maximum CVSS of 7.8. Get it from the Microsoft Update Catalog below, and see where it sits against the rest of the month on the patch tracker.
Update summary
New to these terms? How the Microsoft patching tools fit together, this month's Patch Tuesday summary, and every update ranked by real-world risk.
Senserva AI Opinion for KB5002835
KB5002835 patches three CVEs (CVE-2026-21259, CVE-2026-21258, CVE-2026-21261) across Office Online Server and Office 2019 in both 32-bit and 64-bit editions, with a highest Severity of High at CVSS 7.8. The Office Online Server inclusion is the notable part here, since a shared server component means one host can expose many users rather than individual desktops alone. Neither of these CVEs is in the CISA KEV catalog or linked to ransomware, and the highest EPSS is only 1 percent, so this is patch-on-schedule rather than a drop-everything event.
Do this: Apply KB5002835 to your Office Online Server hosts first, then push it to Office 2019 32-bit and 64-bit desktops through your normal update ring.
AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5002835
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5002835
Senserva began recording day-to-day change history on 2026-07-07, and refreshes it several times a day. Release dates are historical where Microsoft publishes them; revision history is tracked from that date forward, so it does not include changes made before then.
Exploitation and severity
Fixes 3 CVEs. Most severe CVSS 7.8 (High). EPSS exploit probability up to <1%.
Among the lower half of tracked Microsoft updates by EPSS exploit probability.
What to do
Moderate priority: schedule it in your normal patch cycle. Senserva flags whether KB5002835 is missing on your devices.
Check if KB5002835 is installed
Copy-paste PowerShell: one machine, or your whole estate in one pass. No output means the update is not installed.
Get-HotFix covers Windows updates. Office, SharePoint, and Exchange server updates show under installed updates in Programs and Features, or check the Update Catalog history.
CVEs fixed by this update
Sorted exploited-first, then by CVSS. Every CVE links to its Senserva page with the full risk facts, references, and a ready-to-paste AI prompt.
| CVE | Severity | CVSS | EPSS | Exploited |
|---|---|---|---|---|
| CVE-2026-21258 | High | 7.8 | <1% | No |
| CVE-2026-21259 | High | 7.8 | <1% | No |
| CVE-2026-21261 | High | 7.8 | <1% | No |
Affected products
Also released in February 2026
The highest-risk updates from the same release:
The full month, summarized: Microsoft Patch Tuesday.
Authoritative references
See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.