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Dossier · Vulnerability

Actively exploited · CISA KEV · NVD published 2026-05-14

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.

  1. KEV
  2. same day →First PoC
  3. 76 days →First cited attacker

Signals

Exploited in the wild
Yesadded 2026-05-15 · due 2026-05-29. An observation, not a forecast.
EPSS · 30-day forecast
1%Chance of exploitation in the next 30 days, 43th percentile of all CVEs. A forecast; KEV outranks it.
CVSS · NVD · HIGH
8.1CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Internet exposure
not stated by sourcesNo exposure census on this CVE's dispatches.

Exploits

1 known · links only

GitHub PoCs · by trust, then stars1

  1. atiilla/CVE-2026-42897 ↗Trust ok 100

    CVE-2026-42897 - Exchange Health Checker blind spot: outbound IIS URL Rewrite rules silently ignored, making EOMT mitigations invisible in diagnostic reports.

    ★ 5 · created 2026-05-15

Fake proof-of-concept repositories have been used to deliver malware to the researchers who run them. The trust verdict is our engine's heuristic over the repository (account age, what it ships, how its stars arrived); it is a reason to read the code first, not a finding about its author.

On the wire

1 dispatch
  1. Laundry Bear's new Microsoft Exchange attack triggers on email open (CVE-2026-42897)KEV

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