Microsoft Exchange Server Cross-Site Scripting Vulnerability
Microsoft — Microsoft Exchange Server 2016 Cumulative Update 23
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.
8.1
71.2%
Vector breakdown
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N/E:F/RL:O/RC:C
- Published
- May 14, 2026
- Modified
- Aug 10, 2026
- Added to KEV
- May 15, 2026
- Federal patch due
- May 29, 2026
CISA 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.
Weakness classification
Proof-of-concept & exploitation references
Weaponization
Public repositories whose name or description references CVE-2026-42897, found via a live GitHub search at request time. These are community-sourced signals, not a verified working exploit — cross-check each one before relying on it, and treat higher star counts and recent activity as (weak) corroboration, not proof.
No public GitHub repositories referencing CVE-2026-42897 were found at last check. Absence here is not proof no exploit exists — see the references below for vendor advisories and write-ups.
References
How this class of flaw gets exploited
Frequently asked questions
What is CVE-2026-42897?
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 has a CVSS base score of 8.1 out of 10 (CVSS 3.1).
Is CVE-2026-42897 actively exploited in the wild?
Yes. CVE-2026-42897 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added May 15, 2026, meaning CISA has confirmed evidence of active exploitation.
What is the EPSS score for CVE-2026-42897?
71.2% - meaning FIRST.org's EPSS model estimates a 71.2% probability this vulnerability will be exploited in the wild within 30 days (99% percentile among all scored CVEs).
What type of vulnerability is CVE-2026-42897?
CVE-2026-42897 is classified under CWE-79 (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')).
Cross-checked against
Impactr finds and proves whether CVE-2026-42897 — or flaws like it — are actually reachable in your own web apps and APIs, with a reproducible exploit as evidence.