Patch tracker / CVE reference / CVE-2026-45503
CVE-2026-45503
CVE-2026-45503 is a critical severity Microsoft vulnerability with a CVSS score of 9.6. Its EPSS score puts the probability of exploitation in the next 30 days at 70%. Microsoft has shipped the fix: deploy one of the 8 updates below from the Microsoft Update Catalog, and see where this CVE sits against the rest on the patch tracker.
Risk summary
Not in the CISA KEV catalog. EPSS exploit probability 70%. CVSS 9.6 (Critical).
This CVE is among the top 25% of tracked Microsoft CVEs by EPSS exploit probability.
The exploit probability of CVE-2026-45503 is RISING: EPSS 20% to 70% on 2026-08-03.
Drawn by Senserva Vivid from the Senserva change record. Hover any point for its date and value.
- 2026-07-17 CVSS 8.1 to 8.8; EPSS first scored at 5.6%
- 2026-07-24 CVSS 8.8 to 6.5; CVSS 6.5 to 8.8; EPSS 5.6% to 20.3%
- 2026-07-29 CVSS 8.8 to 9.6
- 2026-08-03 EPSS 20.3% to 70.3%
Recorded by Senserva on the dates shown, from CISA KEV and FIRST EPSS. This is what moved and when, which neither the vendor advisory nor NVD publishes.
This is an information disclosure flaw in on-premises Exchange Server carrying a High severity rating with a CVSS score of 8.8, which is unusually elevated for a disclosure-only issue and suggests it can expose sensitive mailbox or configuration data. Exposed systems include Exchange 2016 CU23, Exchange 2019 CU15, and the Subscription Edition RTM, so most organizations still running Exchange on-premises are in scope. It is not in CISA KEV and has no confirmed ransomware use, but the 20 percent EPSS score is meaningfully above baseline for an internet-facing mail platform.
Do this: Apply the Microsoft security update to your Exchange 2016 CU23, 2019 CU15, and Subscription Edition RTM servers, prioritizing any instances with externally reachable OWA or ECP.
AI-generated from public data, 2026-07-25. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for CVE-2026-45503
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Official patch(es) for CVE-2026-45503
High priority: EPSS puts the odds of near-term exploitation high. In Intune or Defender, confirm whether the fixing updates KB5094139, KB5094140, KB5094142, KB5094144, KB5103212, KB5103213, KB5103214, KB5103215 are installed across the affected products. Senserva does this automatically across your tenant and flags every missing patch.
Apply the Microsoft security updates below to fix CVE-2026-45503. 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.
Scope and sources
- Affected products
- Fixed by the same updates
- Authoritative references
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