Microsoft Exchange Server's Outlook Web Access Cross-Site Scripting Flaw Executes Arbitrary JavaScript When Interaction Conditions Are Met; CISA's May 29th KEV Deadline Has Passed

Last refreshed2026-09-27

Status: KEV | Advisory ID: CVE-2026-42897

Key Details

CVE	CVE-2026-42897
Vulnerability Name	Microsoft Exchange Server Cross-Site Scripting Vulnerability
Affected products	Microsoft Microsoft
Exploitation status	Listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating confirmed active exploitation.
Classified as	CWE-79 (Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'))
KEV listing	Added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2026-05-15.
Exploitation prediction (EPSS)	0.52% probability of exploitation in the next 30 days (42% percentile) -- FIRST.org's EPSS model.
Federal remediation deadline	2026-05-29 (CISA KEV, Binding Operational Directive).

Affected Products, Subsystems & Sectors

Vendor	Product	Affected Versions	Patch Status
Microsoft	Microsoft

Vendor

Product

Affected Versions

Patch Status

Microsoft

Subsystems	General OT
Sectors	Multiple

What to Know

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.

What to Do

Monitor Microsoft's web page for any future patch releases.

References

Source	Reference
NVD	https://nvd.nist.gov/vuln/detail/CVE-2026-42897
CVE	https://www.cve.org/CVERecord?id=CVE-2026-42897

Source

Reference

NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-42897

CVE

https://www.cve.org/CVERecord?id=CVE-2026-42897

KEV Required Action

Field	Value
KEV Link	https://www.cisa.gov/known-exploited-vulnerabilities-catalog
Date Added to KEV	2026-05-15
Required Action Due Date	2026-05-29
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.

Field

Value

KEV Link

https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Date Added to KEV

2026-05-15

Required Action Due Date

2026-05-29

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.