Recorded 21 Oct 2026 at 21:47 UTC. This is what ChangeIntel recorded, including the title, summary, facts and links. It is not a statement of the source's current position. See the latest record.

The historical field “Public exploit code” recorded Nuclei detection-template membership. It did not establish exploit availability. The original recorded fields remain below.

The historical “Publicly disclosed: No” field could represent a missing MSRC assessment. It does not establish that the vulnerability was undisclosed. The original recorded fields remain below.

CVEMicrosoft Security Response Center

.NET Information Disclosure Vulnerability

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

What it said

CVE: CVE-2026-58649
Severity: Important
CVSS base score: 6.5
CVSS vector: 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
Impact: Information Disclosure
Exploitation detected: Not reported by MSRC
Publicly disclosed: No
Exploitability: Exploitation Less Likely
Component: .NET
Weakness: CWE-346: Origin Validation Error
Issued by: Microsoft
Customer action: Required: apply the update
Affected products: .NET 10.0 installed on Linux, .NET 10.0 installed on Mac OS, .NET 10.0 installed on Windows, .NET 11.0 installed on Linux, .NET 11.0 installed on Mac OS, .NET 11.0 installed on Windows, .NET 8.0 installed on Linux, .NET 8.0 installed on Mac OS, .NET 8.0 installed on Windows, .NET 9.0 installed on Linux, .NET 9.0 installed on Mac OS, .NET 9.0 installed on Windows, Microsoft Visual Studio 2022 version 17.14, Microsoft Visual Studio 2026 version 18.9
Updates that fix it: KB5126104: .NET 8.0 installed on Linux, .NET 8.0 installed on Mac OS, .NET 8.0 installed on Windows (restart required); KB5126105: .NET 9.0 installed on Linux, .NET 9.0 installed on Mac OS, .NET 9.0 installed on Windows (restart required); KB5126106: .NET 10.0 installed on Linux, .NET 10.0 installed on Mac OS, .NET 10.0 installed on Windows (restart required)
CISA KEV: Not listed in the collected catalog
EPSS: 0.3%; scored 21 Oct 2026
Public exploit code: No Nuclei template listed
Published: 8 Sep 2026 07:00 UTC
Last revised: 8 Sep 2026 07:00 UTC
Revision note: Information published.

Recorded links

Source evidence when recorded

Microsoft security releases: Complete at observationRead 21 Oct 2026 at 21:46 UTC
CISA KEV: Complete at observationRead 21 Oct 2026 at 21:46 UTC
FIRST EPSS: Complete at observationRead 21 Oct 2026 at 21:46 UTC
Public detection templates (Nuclei): Complete at observationRead 21 Oct 2026 at 21:46 UTC

Coverage describes the sources at this observation. A complete read then does not establish their current position.

Page history

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Cite this version

Field-level log (9)

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21 Oct 2026 · 21:47:24 UTC EPSS0.3%; scored 20 Oct 2026 → 0.3%; scored 21 Oct 2026
20 Oct 2026 · 20:53:31 UTC EPSS0.3%; scored 19 Oct 2026 → 0.3%; scored 20 Oct 2026
19 Oct 2026 · 15:12:40 UTC EPSS0.3%; scored 18 Oct 2026 → 0.3%; scored 19 Oct 2026
18 Oct 2026 · 14:54:30 UTC EPSS0.3%; scored 16 Oct 2026 → 0.3%; scored 18 Oct 2026
18 Oct 2026 · 14:54:30 UTC Link: September 2026/security?release=2026-Sep#cves
16 Oct 2026 · 16:13:25 UTC EPSS0.3%; scored 15 Oct 2026 → 0.3%; scored 16 Oct 2026
15 Oct 2026 · 21:30:54 UTC EPSS0.3%; scored 14 Oct 2026 → 0.3%; scored 15 Oct 2026
15 Oct 2026 · 01:07:54 UTC EPSS0.3%; scored 13 Oct 2026 → 0.3%; scored 14 Oct 2026
14 Oct 2026 · 11:22:42 UTC Source coverage: msrc-cvrfIncomplete → Current