Patch tracker / KB5002837
KB5002837: Office Online Server Security Update (February 2026)
KB5002837 is a High security update for Office Online Server, released 2026-02-10. It closes 3 CVEs with a maximum CVSS of 7.8. It is the 15th largest of the 31 updates Microsoft shipped that month, by CVEs closed.
Update summary
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.
A newer security update for Office Online Server has shipped since this one: KB5002884 (2026-08-11). For cumulative update families the newer package includes these fixes, so installing that one is usually the shorter path. Verify against your own update rings before you skip this package.
KB5002837 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. The highest issue rates High at CVSS 7.8, but EPSS sits at 1 percent, none are in CISA KEV, and none are ransomware-linked, so this is a routine hardening update rather than an active-exploitation emergency. The Office Online Server component makes it relevant to organizations running server-side document rendering, not just desktop clients.
Do this: Schedule KB5002837 in your standard patch cycle, prioritizing any Office Online Server hosts alongside Office 2019 desktop installs.
AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5002837
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5002837
- Released
- 2026-02-10
- Last changed
- 2026-02-10
- Changes tracked
- 1
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.
Check if KB5002837 is installed
Elevated PowerShell. No output means it is not installed.
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-2026-21259 | High | 7.8 | <1% | No |
| CVE-2026-21258 | Medium | 5.5 | <1% | No |
| CVE-2026-21261 | Medium | 5.5 | <1% | No |
Scope and sources
- Affected products
- Also released in February 2026
KB5075897
29 CVEs · High · exploitedKB5075899
29 CVEs · High · exploitedKB5075904
24 CVEs · High · exploitedKB5075906
27 CVEs · High · exploitedKB5075912
24 CVEs · High · exploitedKB5075941
26 CVEs · High · exploitedKB5075942
29 CVEs · High · exploitedKB5075943
27 CVEs · High · exploitedThe full month, summarized: Microsoft Patch Tuesday.
- Authoritative references
See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.