CVE-2026-42897

Microsoft: Exchange Server Cross-Site Scripting

As of , CVE-2026-42897 in Microsoft is on CISA's list of exploited vulnerabilities: CISA listed it on . Our patch-first group: Patch soon.

Exploited
Yes: CISA listed it on 15 May 2026
US federal deadline
29 May 202614 days after CISA listed it. US federal civilian agencies must fix it by then.
Used in ransomware campaigns
Not known to CISA
EPSS score
0.01Higher than 42% of the CVEs EPSS scores. EPSS estimates the chance of exploitation activity in the next 30 days.
Public exploit
None foundNeither Metasploit nor Exploit-DB lists one.
Fix
Vendor advice: learn.microsoft.com and msrc.microsoft.comLinks below, from CISA's entry.

What CISA says to do

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

CISA's required action

What the flaw is

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.

CISA's 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.

The CVE record's description, from microsoft

CVE published
14 May 2026
Assigned by
microsoft
CVSS
8.1 High (CVSS 3.1, from the CNA)
CWE-79
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CISA SSVC, exploitation
active
CISA SSVC, automatable
no
CISA SSVC, technical impact
total

Timeline

  1. The CVE record was published.
  2. CISA added it to its list of exploited vulnerabilities.
  3. The US federal deadline to fix it.

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