Patch tracker / CVE reference / CVE-2023-40547

CVE-2023-40547

CVE-2023-40547 is a high severity Microsoft vulnerability with a CVSS score of 8.3. Its EPSS score puts the probability of exploitation in the next 30 days at 41%. Microsoft has shipped the fix: deploy the update below from the Microsoft Update Catalog, and see where this CVE sits against the rest on the patch tracker.

Risk summary

High

8.3

CVSS

41%

EPSS, 30 days

High

Severity

Not in the CISA KEV catalog. EPSS exploit probability 41%. CVSS 8.3 (High).

This CVE is among the top half of tracked Microsoft CVEs by EPSS exploit probability.

Senserva AI Opinion for CVE-2023-40547

This is a flaw in Shim, the boot component that bridges UEFI firmware and the Linux or Windows boot chain, where the HTTP boot path can be exploited for remote code execution before the OS loads and defeat Secure Boot entirely. On the affected Windows 10 Version 1809 and Windows Server 2019 systems it means an attacker positioned to feed the boot process can run code below the operating system. With Severity rated Critical at CVSS 9.8 and a 41 percent EPSS score, this is a pre-boot trust problem, not something endpoint tools running inside the OS can catch.

Do this: Deploy the Shim update to all Windows 10 1809 and Windows Server 2019 hosts and verify that revoked boot components are enforced via updated Secure Boot revocation lists.

AI-generated from public data, 2026-07-23. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2023-40547

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I am an IT admin assessing a vulnerability. Facts for CVE-2023-40547 (source: https://senserva.com/cve/CVE-2023-40547.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2023-40547: High severity Microsoft vulnerability, CVSS 8.3
- EPSS 30-day exploitation probability: 41%
- Actively exploited (CISA KEV): no
- Fixed by: KB5041592
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) What to patch or mitigate first. 4) How to check whether my devices are exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch this cycle

Not confirmed exploited yet, but the 30-day exploit probability is high (EPSS 41%).

Fixed by KB5041592. Download from the Microsoft Update Catalog, or deploy via Windows Update, Intune, or WSUS.

Do this now: Patch in this maintenance window; do not let it slip to the next one.

Official patch(es) for CVE-2023-40547

Elevated priority: high severity or a meaningful exploitation probability, sooner if an affected product is internet-facing. In Intune or Defender, confirm whether the fixing update KB5041592 are installed across the affected products. Senserva does this automatically across your tenant and flags every missing patch.

Apply the Microsoft security update below to fix CVE-2023-40547. Each KB page carries the Microsoft Update Catalog download, Microsoft's known issues for the update, a copy-paste PowerShell check for whether it is installed, and the Senserva AI read.

KB5041592

Scope and sources

Affected products

Fixed by the same update

CVE-2024-38106 CVE-2024-38107 CVE-2024-38178 CVE-2024-38193 CVE-2024-38140 CVE-2024-38143 CVE-2024-38199 CVE-2024-38114

Authoritative references

Official CVE record (cve.org)NVD detail Microsoft MSRC FIRST.org EPSS

Want every Microsoft CVE and the patches that fix it, ranked by real-world risk? See the Microsoft Patch Tracker.