CVE-2026-69378 Microsoft Exchange Server Denial of Service Vulnerability
An unauthorized attacker can cause a denial of service in Microsoft Exchange Server via uncontrolled recursion, requiring administrators to apply vendor patches.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-69378?
CVE-2026-69378 is a high-severity denial of service vulnerability in Microsoft Exchange Server, published on 8 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Uncontrolled recursion in Microsoft Exchange Server allows an unauthorized attacker to deny service over a network.
Weakness: CWE-674
Which versions are affected by CVE-2026-69378?
It affects 2 products.
Products include Microsoft Exchange Server, Microsoft Exchange Server Subscription Edition.
How do I fix CVE-2026-69378?
No fix has been published for CVE-2026-69378 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-69378 being exploited?
There is no known exploitation of CVE-2026-69378 in the wild and no public exploit code.
Other vulnerabilities in Microsoft Exchange Server
- CVE-2024-21410 Microsoft Exchange Server Privilege Escalation
- CVE-2021-34473 Microsoft Exchange Server Remote Code Execution
- CVE-2021-26855 Microsoft Exchange Server Remote Code Execution
- CVE-2021-34523 Microsoft Exchange Server Privilege Escalation
- CVE-2023-21529 Microsoft Exchange Server Deserialization of Untrusted Data
Sources
Also known as GHSA-hp6f-8h4f-5pjq.