Patch tracker / KB5002891
KB5002891: Microsoft SharePoint Server 2019 Security Update (August 2026)
KB5002891 is a Critical security update for Microsoft SharePoint Server 2019, released 2026-08-11. It closes 40 CVEs with a maximum CVSS of 9.8. At least one of them is actively exploited (CISA KEV), so this is a deploy-first update. The most likely of them to be attacked is CVE-2026-70306, which FIRST.org rates at 77% probability of exploitation in the next 30 days.
Update summary
Fixes 40 CVEs. At least one is actively exploited (CISA KEV). Most severe CVSS 9.8 (Critical). EPSS exploit probability up to 77%. Among the top 10% of tracked Microsoft updates by EPSS exploit probability.
Microsoft documents 1 known issue with this update.
- Customers in multi-front-end SharePoint farms with Trusted Provider or Forms authentication may face repeated authentication prompts or multiple...
KB5002891 patches 39 CVEs across SharePoint Server 2016, 2019, and Subscription Edition, topping out at Critical severity with a CVSS of 9.8 and one CVE already listed in the CISA Known Exploited Vulnerabilities catalog. On-premises SharePoint farms are directly exposed, and with a 57 percent EPSS the highest-risk flaw is realistically going to see broad exploitation attempts. The confirmed KEV entry means at least one of these bugs is being used in the wild now, though none are currently tied to ransomware campaigns.
Do this: Apply KB5002891 to all on-premises SharePoint 2016, 2019, and Subscription Edition servers now, prioritizing internet-facing farms because of the KEV-listed CVE.
AI-generated from public data, 2026-07-25. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5002891
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5002891
- Released
- 2026-07-14
- Last changed
- 2026-08-11
- Changes tracked
- 6
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.
The strongest signal is the CVE count rising from 39 to 40 on 2026-08-11, a single confirmed addition. This is a small upward move, showing the fix scope for KB5002891 grew by one on that date. For an IT admin today, treat this as an active update worth reviewing and scheduling for deployment.
- 2026-08-11 CVEs fixed 39 to 40
Recorded by Senserva on the dates shown, from the MSRC release feed. This is what moved and when, which neither the vendor advisory nor NVD publishes.
Check if KB5002891 is installed
Elevated PowerShell. No output means it is not installed.
Known issues, from Microsoft
Quoted from Microsoft's support article for KB5002891 (checked 2026-08-11). Verify against the article before acting.
Customers in multi-front-end SharePoint farms with Trusted Provider or Forms authentication may face repeated authentication prompts or multiple sign-ins. This should not impact customers who have configured farms with Windows authentication. As a mitigation, configuring sticky sessions on the reverse proxy will address the majority of scenarios. Microsoft is working on a fix in the subsequent product update. While disabling SessionCookieTransformProtectionEnabled may appear to work around the issue, Microsoft does not recommend it. This setting safeguards authentication and turning it off can expose the farm to security vulnerabilities.
When a workflow status link is selected, WrkStat.aspx displays the following error message:
The WorkflowInstanceID parameter is invalid.
To workaround this issue, see Workflow status links fail after installing the July 2026 CU.
Customers who install the SharePoint 2016 July Public Update might find that Office Online Server can't render or edit documents. To mitigate this problem, register the farm's STS signing certificate (public key only) as a trusted token issuer, and then recycle IIS on every server in the farm by using the following steps:
# Get STS certificate
$stsm = Get-SPSecurityTokenServiceConfig
$live = $stsm.LocalLoginProvider.SigningCertificate
# Export public certificate only (without private key)
$bytes = $live.Export("Cert") ...
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-2026-50522 | Critical | 9.8 | 77% | KEV |
| CVE-2026-56164 | Medium | 5.3 | 77% | KEV |
| CVE-2026-70306 | Critical | 9.3 | 77% | No |
| CVE-2026-55040 | Critical | 9.1 | 77% | No |
| CVE-2026-55052 | High | 8.8 | 77% | No |
| CVE-2026-58277 | High | 8.8 | 77% | No |
| CVE-2026-55045 | High | 8.4 | 77% | No |
| CVE-2026-55032 | High | 7.8 | 77% | No |
| CVE-2026-55033 | High | 7.8 | 77% | No |
| CVE-2026-55038 | High | 7.8 | 77% | No |
| CVE-2026-55055 | High | 7.8 | 77% | No |
| CVE-2026-55125 | High | 7.8 | 77% | No |
| CVE-2026-55127 | High | 7.8 | 77% | No |
| CVE-2026-55128 | High | 7.8 | 77% | No |
| CVE-2026-55130 | High | 7.8 | 77% | No |
| CVE-2026-55132 | High | 7.8 | 77% | No |
| CVE-2026-55134 | High | 7.8 | 77% | No |
| CVE-2026-55021 | High | 7.3 | 77% | No |
| CVE-2026-55034 | High | 7.3 | 77% | No |
| CVE-2026-55126 | High | 7.3 | 77% | No |
| CVE-2026-54108 | Medium | 6.5 | 77% | No |
| CVE-2026-55051 | Medium | 6.5 | 77% | No |
| CVE-2026-55026 | Medium | 6.2 | 77% | No |
| CVE-2026-55023 | Medium | 5.5 | 77% | No |
| CVE-2026-55027 | Medium | 5.5 | 77% | No |
| CVE-2026-55028 | Medium | 5.5 | 77% | No |
| CVE-2026-55035 | Medium | 5.5 | 77% | No |
| CVE-2026-55047 | Medium | 5.5 | 77% | No |
| CVE-2026-55050 | Medium | 5.5 | 77% | No |
| CVE-2026-55121 | Medium | 5.5 | 77% | No |
| CVE-2026-55124 | Medium | 5.5 | 77% | No |
| CVE-2026-55142 | Medium | 5.5 | 77% | No |
| CVE-2026-56192 | Medium | 5.5 | 77% | No |
| CVE-2026-56157 | Medium | 5.4 | 77% | No |
| CVE-2026-55016 | Medium | 4.6 | 77% | No |
| CVE-2026-55019 | Medium | 4.6 | 77% | No |
| CVE-2026-55020 | Medium | 4.6 | 77% | No |
| CVE-2026-55030 | Medium | 4.6 | 77% | No |
| CVE-2026-55135 | Medium | 4.6 | 77% | No |
| CVE-2026-62826 | Medium | 4.6 | 77% | No |
What the press says about this update
Trusted-source coverage of the CVEs this update fixes, pulled live from their own feeds.
Scope and sources
- Affected products
- Also released in August 2026
KB5002882
39 CVEs · Critical · exploitedKB5002883
40 CVEs · Critical · exploitedKB5120228
212 CVEs · Critical · exploitedKB5120229
194 CVEs · Critical · exploitedKB5120233
214 CVEs · Critical · exploitedKB5120238
182 CVEs · Critical · exploitedKB5120240
170 CVEs · Critical · exploitedKB5120242
194 CVEs · Critical · 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.