Microsoft Exchange Server Privilege Escalation Vulnerability
CVE-2024-21410 is a security vulnerability in Microsoft Exchange Server, added to CISA KEV on February 15, 2024. Patch order: second of four.
What is CVE-2024-21410?
Microsoft Exchange Server contains an unspecified vulnerability that allows for privilege escalation.
VulnCheck tracked exploitation 1 day before CISA's KEV listing. VulnCheck's broader catalog of in-the-wild exploitation evidence picked this up before it landed on CISA's formal list. Per-CVE fact about this entry; not a population claim about lead time in general.
Who is affected by CVE-2024-21410?
Affects anyone running on-premises Microsoft Exchange Server. If you have Exchange in your office (as opposed to Microsoft 365 hosted email), it's the mail server holding all internal email — full compromise reads every conversation it stores.
What should I do about CVE-2024-21410?
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
If you don't have someone in-house to verify the patch deployed across every endpoint — or you're not sure whether you're affected — that's exactly the kind of triage we do. Request a free review.
Insurance readiness
Your insurer will ask if this is patched.
Unpatched entries on CISA's Known Exploited Vulnerabilities list are exactly what cyber-insurance carrier questionnaires probe for, and knowing which controls they check is how you keep a renewal from stalling.
Get the free carrier questionnaire →Severity
CVSS base score: 9.8 — CRITICAL
Weakness classification: CWE-287
Microsoft fix
Microsoft Exploitability Index (assessed at update release): Exploitation Detected
Microsoft has confirmed in-the-wild exploitation in the latest software release. This aligns with CISA's listing of this CVE.
Vendor workaround
Vendor-published mitigation
The following mitigating factors might be helpful in your situation:
Consult the Exchange Extended Protection documentation and use the ExchangeExtendedProtectionManagement.ps1 script to turn on the Extended Protection for Authentication (EPA) for Exchange Servers.
A workaround reduces exposure while you patch — it is not a substitute for the update. Install the fix above as soon as you can.
CISA due date
CISA's listed due date: March 7, 2024.
Federal civilian agencies work under CISA's Binding Operational Directive 26-04, which replaced BOD 22-01 on June 10, 2026. It sets the deadline for each affected system by:
- How exposed that system is to the internet
- Whether the attack can be automated
- How much control it gives an attacker
Its table gives catalogued vulnerabilities 3 or 14 days.
None of this binds a private business, but treat the date as a strong recommendation, especially if you handle regulated data (HIPAA, GLBA, ABA model rules).
EPSS
EPSS score: 12.6% — higher than 96% of all scored CVEs.
EPSS estimates the probability of exploitation activity in the next 30 days. Every entry on this site is already confirmed exploited, so read it as relative urgency among the things you still have open, not as permission to wait.
Other exploited Microsoft Exchange Server entries
More CISA KEV entries for Microsoft Exchange Server. Same product line, same actively-exploited status.
Source
This entry comes from CISA's Known Exploited Vulnerabilities catalog, public US-Government data we pull daily. The plain-language framing and the what-to-do guidance above are ours. View the original entry on cisa.gov.