CVE-2026-42897: listed in the CISA KEV catalog

CVE-2026-42897 · CVSS 8.1 HIGH · KEV 2026-05-15 · patch available

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.

Is CVE-2026-42897 exploited?

• Listed in the CISA KEV catalog on 2026-05-15.
• Federal remediation due 2026-05-29.
• Past that date by 154 days.
• Public exploit code: none found in monitored sources.

Which products and versions are affected?

• Microsoft · Microsoft Exchange Server 2016 Cumulative Update 23 · >= 15.01.0.0, < 15.01.2507.069
• Microsoft · Microsoft Exchange Server 2019 Cumulative Update 14 · >= 15.02.0.0, < 15.02.1544.041
• Microsoft · Microsoft Exchange Server 2019 Cumulative Update 15 · >= 15.02.0.0, < 15.02.1748.046
• Microsoft · Microsoft Exchange Server Subscription Edition RTM · >= 15.02.0.0, < 15.02.2562.043

Is there a patch?

Yes. Update to one of these or later:

From Microsoft's CVE record · Microsoft advisory

• KB5094144
• KB5094142
• KB5094140
• KB5094139

From Microsoft's Security Update Guide · Microsoft advisory

What PlainSec published about CVE-2026-42897

• OWA access now survives resets and reimaging (2026-07-31)

Primary sources

• NVD record
• CISA KEV catalog
• Microsoft KB5094139
• Microsoft advisory

What this record does not say

• No EPSS score.

KEV and EPSS are re-checked daily. Record last updated 2026-08-11.