// CVE

CVE-2026-42897

High 8.1 Exploited (KEV)

Microsoft Microsoft Exchange Server 2016 Cumulative Update 23

8.1CVSS
70%EPSS
YesCISA KEV

Summary

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.

Published: 2026-05-14 · In KEV since: 2026-05-15

Analysis

🔴 Critical — actively exploited

How it's exploited: Exploitable over the network (internet-reachable), unauthenticated, if the victim interacts (open a file/click), and with low complexity.

Impact: Confidentiality high · Integrity high · Availability none.

Status: Active exploitation confirmed by CISA (KEV).

How to defend:
  • Patch now: it is in CISA's actively-exploited catalog (KEV), with a deadline.
  • Reduce exposure: keep it off the internet; firewall, VPN or network segmentation.
  • Awareness: the attack needs victim interaction (phishing/file).
  • Detect: turn this CVE into detection rules.

CVSS vector

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

The vector encodes how it's exploited (translated above, in the analysis). Break it down in the CVSS tool →

🔗 NVD record CISA KEV 🌉 CVE → detection 🎯 Am I exposed? ⚖️ Prioritize patch

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Sources: CISA KEV · EPSS · FIRST.org · NVD. Analysis derived from the CVSS vector and exploitation status (no AI). Informational; always verify against the vendor's official advisory.