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Vulnerabilities/CVE-2026-58649Public Intelligence Dossier
Source: Microsoft · Limited verification•Last verified: •Collection Degraded
CVE-2026-58649Unknown / EvaluatingImportant (raw)CVSS 6.5

.NET 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
0.3%0.003
Percentile18th
Weakness type
—
No further CWE recorded
Remediation
Patch status unknown
KB5126104, KB5126105, KB5126106

Why It Matters

Analysis dossier

Why It Matters

Origin validation error in .NET allows an unauthorized attacker to disclose information over a network.

SOC priority

Review

Actively exploited

No

Publicly disclosed

Unknown

Risk basis: No confirmed exploitation signal in current enrichment

Affected Products & Remediation

14 source-backed products
Affected products and versions (source)
  • Microsoft Visual Studio 2022 version 17.14 · version range not provided by source · Microsoft MSRC · Source
  • .NET 11.0 installed on Linux · version range not provided by source · Microsoft MSRC · Source
  • .NET 11.0 installed on Mac OS · version range not provided by source · Microsoft MSRC · Source
  • .NET 8.0 installed on Windows · version range not provided by source · Microsoft MSRC · Source
  • .NET 8.0 installed on Mac OS · version range not provided by source · Microsoft MSRC · Source
  • .NET 8.0 installed on Linux · version range not provided by source · Microsoft MSRC · Source
  • .NET 9.0 installed on Mac OS · version range not provided by source · Microsoft MSRC · Source
  • .NET 9.0 installed on Windows · version range not provided by source · Microsoft MSRC · Source
  • .NET 9.0 installed on Linux · version range not provided by source · Microsoft MSRC · Source
  • Microsoft Visual Studio 2026 version 18.9 · version range not provided by source · Microsoft MSRC · Source
  • .NET 11.0 installed on Windows · version range not provided by source · Microsoft MSRC · Source
  • .NET 10.0 installed on Windows · version range not provided by source · Microsoft MSRC · Source
  • .NET 10.0 installed on Linux · version range not provided by source · Microsoft MSRC · Source
  • .NET 10.0 installed on Mac OS · version range not provided by source · Microsoft MSRC · Source
Recorded patch / KBKB5126104, KB5126105, KB5126106

Vendor or catalog guidance (source)

  • Microsoft MSRC: Release Notes
  • Microsoft MSRC: Install the security update KB5126104 listed by MSRC
  • Microsoft MSRC: Install the security update KB5126105 listed by MSRC
  • Microsoft MSRC: Install the security update KB5126106 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 microsoft-enterprise (Affected product: .NET 8.0 installed on Windows, Vendor: Microsoft); user-interaction-client (CVSS AV:N, CVSS UI:R)

Exposure

  1. Identify affected Microsoft products and compare local builds with the MSRC advisory.Telemetry: DeviceTvmSoftwareVulnerabilities · The MSRC product/build mapping establishes applicability. · Rule microsoft-enterprise
  2. 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 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
Show more (2)

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 KB or mitigation on matching assets.Telemetry: DeviceTvmSoftwareVulnerabilities · A post-update inventory check verifies remediation. · Rule microsoft-enterprise

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.