CVE-2026-42897: Microsoft Exchange Server Cross-Site Scripting Vulnerability
CVE-2026-42897 is a Severity not scored in source feed flaw in Microsoft Microsoft. 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. It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-05-15), meaning it is being actively exploited. The fix: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Source: CISA Known Exploited Vulnerabilities Catalog. Data as of 2026-06-13.
Vulnerability details
| Field | Value |
|---|---|
| CVE ID | CVE-2026-42897 |
| Vulnerability | Microsoft Exchange Server Cross-Site Scripting Vulnerability |
| Vendor / product | Microsoft — Microsoft |
| CVSS base score | Not in source feed |
| Severity | — |
| Weakness (CWE) | CWE-79 |
| Added to CISA KEV | 2026-05-15 |
| CISA remediation due | 2026-05-29 |
| Known ransomware use | Unknown |
Source: CISA Known Exploited Vulnerabilities Catalog. Data as of 2026-06-13.
What is the risk?
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.
How to remediate CVE-2026-42897
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
U.S. federal civilian agencies were required to remediate this vulnerability by 2026-05-29 under CISA Binding Operational Directive 22-01. Private organizations should treat it with comparable urgency.
References
Frequently asked questions
What is CVE-2026-42897?
CVE-2026-42897 is a vulnerability in Microsoft Microsoft: 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.
How severe is CVE-2026-42897?
The CISA KEV catalog does not publish a CVSS base score for this entry. Check the NVD record for the official score. Its presence in the KEV catalog means it is confirmed to be exploited in the wild.
Is CVE-2026-42897 being exploited in the wild?
Yes. It appears in the CISA Known Exploited Vulnerabilities (KEV) catalog, which only lists vulnerabilities with reliable evidence of active exploitation. It was added on 2026-05-15.
How do I fix CVE-2026-42897?
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Related vulnerabilities
Last updated: 2026-06-13