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Vulnerabilities/CVE-2026-42897Public Intelligence Dossier
Source: microsoft · Limited verification•Last verified: •Collection Degraded
CVE-2026-42897ListedHIGH (raw)CVSS 8.1CWE-79

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: 14 May 2026•Last updated: 17 Jun 2026, 04:18 PM IST•Source identifier: secure@microsoft.com
Dossier completeness: source-provided sections 3 / 3 · rule guidance available. Missing source facts count as incomplete.
Official source
CISA KEV catalog
Listed
Added15 May 2026
Due29 May 2026
RansomwareUnknown
CVSS score
8.1HIGH (raw)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Metric sourcesecure@microsoft.com
EPSS probability
—
Percentile—
Weakness type
CWE-79
No further CWE recorded
Remediation
Patch status unknown
No fixed version or KB recorded

Why It Matters

Analysis dossier

Why It Matters

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.

SOC priority

Immediate Attention

Actively exploited

Yes

Publicly disclosed

Unknown

Risk basis: CISA KEV exploitation signal; Microsoft or Microsoft-managed product relevance; HIGH severity; Known exploitation signal from CISA KEV or ransomware metadata

Affected Products & Remediation

2 source-backed products
Affected products and versions (source)
  • microsoft exchange server · 2016; 2019; subscription edition < 15.02.2562.043 · NVD CPE · Source
  • microsoft exchange server subscription edition · < 15.02.2562.043 · NVD CPE · Source
Recorded patch / KBNot provided by source

Vendor or catalog guidance (source)

  • CISA KEV: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Known exploitation (source facts)

Only what a source states. Unknown means no source has said either way; it is not "not exploited".

CISA KEV
Listed
Exploited (source statement)
Yes
Publicly disclosed (source)
Unknown

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.

Suggested hunting (rule-based inference)

SecOps Signal recommendation (rule-based inference). These steps are hunting hypotheses from the vulnerability class; they do not state or imply that exploitation occurred here or anywhere.

Matched kev-network-exposure (CVSS AV:N, CISA KEV Listed); microsoft-enterprise (Affected product: microsoft exchange server, Vendor: microsoft)

Exposure

  1. Identify assets with the exact CVE and confirm the affected product/version against the advisory.Telemetry: DeviceTvmSoftwareVulnerabilities · KEV listing raises urgency, but inventory is needed to establish local exposure. · Rule kev-network-exposure
  2. Identify affected Microsoft products and compare local builds with the MSRC advisory.Telemetry: DeviceTvmSoftwareVulnerabilities · The MSRC product/build mapping establishes applicability. · Rule microsoft-enterprise

Exploitation evidence

  1. Review relevant edge or application access logs for unusual requests around the advisory window.Telemetry: CommonSecurityLog · Log review is a hunting hypothesis; KEV listing alone does not show local exploitation. · Rule kev-network-exposure
Show more (2)

Exploitation evidence

  1. Review the advisory's documented behavior on matching hosts before selecting a hunt.Telemetry: DeviceProcessEvents · Product family alone does not justify a CVE-specific detection. · Rule microsoft-enterprise

Response

  1. Recheck the affected assets after the source-stated mitigation or update is applied.Telemetry: DeviceTvmSoftwareVulnerabilities · A follow-up inventory check verifies local remediation. · Rule kev-network-exposure

CISA KEV Record

Catalog entry
15 May 2026
Required action due
29 May 2026
Known ransomware use
Unknown

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Change History & Source Data

— No recorded material change

CNA / source
secure@microsoft.com
Record status · verification
NEW · Microsoft primary source linked; CISA KEV confirmed
CPE
cpe:2.3:a:microsoft:exchange_server:2016:-:*:*:*:*:*:*, cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_1:*:*:*:*:*:*, cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_10:*:*:*:*:*:*, cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_11:*:*:*:*:*:*, cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_12:*:*:*:*:*:*, cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_13:*:*:*:*:*:*, cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_14:*:*:*:*:*:*, cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_15:*:*:*:*:*:*, cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_16:*:*:*:*:*:*, cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_17:*:*:*:*:*:*

Evidence & Provenance

4 public sources
CISA KEV CatalogAdded 2026-05-15msrc.microsoft.comSource recordnvd.nist.govSource recordcisa.govSource record

Linked by the query's stored exact CVE association. Review required tables and validation status before use.

Detection Hunting Query
Target: DeviceTvmSoftwareVulnerabilities•Defender XDR
Detect endpoints exposed to CVE-2026-42897
Purpose: Exposure assessment (Category: Exposure Check)Why linked: Query metadata names CVE-2026-42897
DeviceTvmSoftwareVulnerabilities| where CveId == "CVE-2026-42897"| project DeviceId, DeviceName, OSPlatform, OSVersion, SoftwareVendor, SoftwareName, SoftwareVersion, CveId, VulnerabilitySeverityLevel, RecommendedSecurityUpdate, RecommendedSecurityUpdateId| sort by VulnerabilitySeverityLevel desc
Schema Checked · Not runtime validatedSource: SecOps Signal deterministic template · Limited verificationStatic screening: Passed structure and schema checks; tenant execution is not verified.
Open KQL Library
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Correlated briefings

SecOps Signal surfaces public advisory facts only. A missing value means the source has not published it, not that your environment is unaffected. No tenant inventory is connected.