Vulnerability · Published Jul 14, 2026 · Assigned by microsoft
CVE-2026-55009Microsoft Exchange Server Elevation of Privilege Vulnerability
High 7.8
In plain English
A high-severity unsafe deserialization in Microsoft Exchange Server 2016 Cumulative Update 23 from Microsoft. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 2.5% (higher than 85% of all known vulnerabilities).
Severity (CVSS 3.1)7.8High
Exploit odds (30 days)2.5%top 15.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 23 | 15.01.0.0 – before 15.01.2507.071 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 14 | 15.02.0.0 – before 15.02.1544.043 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 15 | 15.02.0.0 – before 15.02.1748.048 |
| Microsoft | Microsoft Exchange Server Subscription Edition RTM | 15.02.0.0 – before 15.02.2562.045 |
Weakness: CWE-502 · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
References
- Microsoft Exchange Server Elevation of Privilege Vulnerability vendor-advisory, patch