CVEs / CVE-2026-42897
CVE-2026-42897: Microsoft Exchange Server Cross-Site Scripting Vulnerability
- Known exploited in the CISA KEV catalog since 15 May 2026
- medium 6.1 CVSS 3.1 (NVD)
- EPSS 70.6% chance of exploitation in the next 30 days, higher than 99% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
Microsoft Exchange Server contains a cross-site scripting vulnerability during web page generation in Outlook Web Access and when certain interaction conditions are met, arbitrary JavaScript can be executed in the browser context.
Description
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.
Affected and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| Microsoft Microsoft Exchange Server 2016 Cumulative Update 23 | from 15.01.0.0, before 15.01.2507.069 | 15.01.2507.069 |
| Microsoft Microsoft Exchange Server 2019 Cumulative Update 14 | from 15.02.0.0, before 15.02.1544.041 | 15.02.1544.041 |
| Microsoft Microsoft Exchange Server 2019 Cumulative Update 15 | from 15.02.0.0, before 15.02.1748.046 | 15.02.1748.046 |
| Microsoft Microsoft Exchange Server Subscription Edition RTM | from 15.02.0.0, before 15.02.2562.043 | 15.02.2562.043 |
Exploitation
| In CISA KEV since | 15 May 2026 |
|---|---|
| Due date for US federal agencies | 29 May 2026 |
| Used in ransomware campaigns | Unknown |
| Required action | Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. |
Severity
| CVSS 3.1 | 6.1 mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:NScored by NVD |
|---|---|
| Weakness | CWE-79 |
References
- CVE-2026-42897 on NVD
- CVE-2026-42897 in the CISA KEV catalog
- https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-42897 (cited by CISA)
- https://learn.microsoft.com/en-us/exchange/plan-and-deploy/post-installation-tasks/security-best-practices/exchange-emergency-mitigation-service (cited by CISA)
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42897 Mitigation, Vendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-42897 US Government Resource
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.