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
- Published
- May 14, 2026
- Modified
- Jun 17, 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
Affected packages
Proof-of-concept & exploitation references
1 foundWeaponization
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.
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).
Is there exploit tooling available for CVE-2026-42897?
We found 1 public GitHub repository referencing CVE-2026-42897, though none matched a known Nuclei template or Metasploit module at last check. Review each one before relying on it - see the proof-of-concept section above.
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
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