Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:H) | High complexity |
| Privileges required (PR:N) | No privileges required |
| User interaction (UI:R) | A user must take an action |
| Scope (S:U) | Scope unchanged |
| Confidentiality (C:H) | High confidentiality impact |
| Integrity (I:H) | High integrity impact |
| Availability (A:H) | High availability impact |
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
About Microsoft Exchange Server
CVE-2026-45583 affects Microsoft Exchange Server, a product from Microsoft. Before acting, confirm where Microsoft Exchange Server runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: Improper control of generation of code ('code injection') in Microsoft Exchange Server allows an unauthorized attacker to execute code over a network.
The weakness class is Code Injection. Attacker input is executed as program code.
Based on its CVSS vector, the flaw can be reached over the network, needs no login, and relies on a user taking an action. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Microsoft Exchange Server |
| Affected versions | Exchange Server 2016; Exchange Server 2019; Exchange Server Subscription Edition before 15.02.2562.043 |
| Published | Jun 9, 2026 |
| Last modified | Jul 28, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | secure@microsoft.com |
How to detect it
- Inventory every instance of Microsoft Exchange Server and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Microsoft Exchange Server named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Microsoft Exchange Server to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-94: Code Injection More CVEs with this weakness
Technical References
Frequently asked questions
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