CVE-2026-55008Critical
Microsoft Exchange Server Spoofing Vulnerability
Assessment
Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.
- Severity
- Critical
- CVSS base score
- 9.6CVSS:3.1/
AV:N/ AC:L/ PR:N/ UI:R/ S:C/ C:H/ I:H/ A:H/ E:U/ RL:O/ RC:C - Impact
- Spoofing
- EPSS, next 30 days
- 0.9%Higher than 56.9% of scored CVEs · FIRST model run 26 Sep 2026 · about EPSS
- Exploitability
- Exploitation More Likely
- Publicly disclosed
- No
- Customer action
- Required: apply the update
- Component
- Microsoft Exchange Server
- Weakness
- CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- Issued by
- Microsoft
- Published
- 14 Jul 2026 · July 2026
- Last revised
- 14 Jul 2026
Updates that fix it
4 KBs| KB | Type | Restart | Applies to | Other CVEs |
|---|---|---|---|---|
| KB5103212 | Security Update | Required | Microsoft Exchange Server Subscription Edition RTM | All CVEs in KB5103212 |
| KB5103213 | Security Update | Required | Microsoft Exchange Server 2019 Cumulative Update 15 | All CVEs in KB5103213 |
| KB5103214 | Security Update | Required | Microsoft Exchange Server 2019 Cumulative Update 14 | All CVEs in KB5103214 |
| KB5103215 | Security Update | Required | Microsoft Exchange Server 2016 Cumulative Update 23 | All CVEs in KB5103215 |
Affected products
ESU, Server Software4 affected products
- Microsoft Exchange Server 2016 Cumulative Update 23
- Microsoft Exchange Server 2019 Cumulative Update 14
- Microsoft Exchange Server 2019 Cumulative Update 15
- Microsoft Exchange Server Subscription Edition RTM