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Vulnerabilities/CVE-2026-66306Public Intelligence Dossier
Source: Microsoft · Limited verification•Last verified: •Collection Degraded
CVE-2026-66306Unknown / EvaluatingImportant (raw)CVSS 6.5

Skype for Business Information Disclosure Vulnerability

Published: 08 Sept 2026•Last updated: 08 Sept 2026, 12:30 PM IST•Source identifier: Unknown
Dossier completeness: source-provided sections 3 / 3 · rule guidance available. Missing source facts count as incomplete.
Official source
CISA KEV catalog
Unknown
KEV status was not determined.
CVSS score
6.5Important (raw)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C
Metric sourceMicrosoft MSRC CVRF
EPSS probability
0.9%0.009
Percentile60th
Weakness type
—
No further CWE recorded
Remediation
Patch status unknown
KB5123300, KB5123287, KB5123301

Why It Matters

Analysis dossier

Why It Matters

Generation of error message containing sensitive information in Skype for Business allows an unauthorized attacker to disclose information over a network.

SOC priority

Medium

Actively exploited

No

Publicly disclosed

Unknown

Risk basis: No confirmed exploitation signal in current enrichment

Affected Products & Remediation

3 source-backed products
Affected products and versions (source)
  • Skype for Business Server 2019 CU8 · version range not provided by source · Microsoft MSRC · Source
  • Skype for Business Server Subscription Edition CU1 · version range not provided by source · Microsoft MSRC · Source
  • Skype for Business Server 2015 CU13 · version range not provided by source · Microsoft MSRC · Source
Recorded patch / KBKB5123300, KB5123287, KB5123301

Vendor or catalog guidance (source)

  • Microsoft MSRC: Install the security update KB5123300 listed by MSRC
  • Microsoft MSRC: Install the security update KB5123287 listed by MSRC
  • Microsoft MSRC: Install the security update KB5123301 listed by MSRC

Known exploitation (source facts)

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

CISA KEV
Unknown
Exploited (source statement)
No
Publicly disclosed (source)
Unknown

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 user-interaction-client (CVSS AV:N, CVSS UI:R)

Exposure

  1. Identify endpoints reporting this CVE, especially those used for email and web browsing.Telemetry: DeviceTvmSoftwareVulnerabilities · A network vector that needs user interaction points at user-facing client software. · Rule user-interaction-client

Exploitation evidence

  1. Review unusual child processes started by the affected client application on affected endpoints.Telemetry: DeviceProcessEvents · Hunting hypothesis from the CVSS vector; it does not show that exploitation occurred. · Rule user-interaction-client

Response

  1. Confirm the source-stated update on affected endpoints.Telemetry: DeviceTvmSoftwareVulnerabilities · A follow-up inventory check verifies remediation. · Rule user-interaction-client

CISA KEV Record

CISA KEV status was not determined for this record.

Change History & Source Data

— No recorded material change

CNA / source
Unknown
Record status · verification
UPDATED · Unknown
CPE
Unknown

Evidence & Provenance

1 public source
api.msrc.microsoft.comSource record
Detection Hunting Query

— No published hunting query names this record. Browse community and library queries instead.

Open KQL Library

Correlated briefings

Microsoft Security Update Guide · Limited verificationSeptember 2026 Security UpdatesPublished 08 Sept 2026
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.