CVE-2026-42897
Microsoft Exchange Server Cross-Site Scripting Vulnerability
Microsoft Microsoft
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.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 15 May 2026. US federal agencies were required to remediate it by 29 May 2026.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 70.3%, which is higher than 99.3% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Frequently asked questions
Is CVE-2026-42897 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2026-42897.
What does CVE-2026-42897 affect?
CVE-2026-42897 affects Microsoft Microsoft. 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.
How severe is CVE-2026-42897?
CVE-2026-42897 is rated HIGH with a CVSS base score of 8.1. EPSS puts the probability of exploitation in the next 30 days at 70.3%, higher than 99.3% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 29 May 2026.
How should organisations respond to CVE-2026-42897?
Apply the vendor patch for Microsoft Microsoft as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.