Threats / Microsoft / CVE-2026-42897
CVE-2026-42897
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Microsoft vulnerability
Microsoft Exchange Server contains a cross-site scripting vulnerability in Outlook Web Access that allows arbitrary JavaScript execution in the browser context when certain interaction conditions are met.
Verdict
Today item — known-exploited.
A reflected or stored XSS vulnerability in Exchange Server's web interface enables attackers to execute malicious scripts in user browsers, potentially compromising session tokens, credentials, or sensitive email data without requiring network access beyond the web application.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
5 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-05-15).
Probability (EPSS)
EPSS 0.02509 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Microsoft, Microsoft. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-79 Cross-site Scripting (XSS) — weakness family: Web / client.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious URL or inject payload into Exchange Server content that executes JavaScript in a victim's browser when they access Outlook Web Access.
Business
User credentials, session tokens, or email contents are compromised, leading to unauthorized access to sensitive corporate communications and potential data exfiltration.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I use the XSS vulnerability to redirect users to phishing pages or capture their authentication details through script execution in the trusted application context.
Business
Attackers gain legitimate-looking access to email systems, enabling business email compromise, fraud, or lateral movement into corporate networks.
3
Lateral reach — past segmentation narrative 3
Attacker
I execute JavaScript to modify email content, inject malware links, or alter forwarding rules within the victim's mailbox through the web interface.
Business
Email integrity is compromised; malware distribution or business email compromise attacks propagate through trusted internal communications channels.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05