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Fencer Vulns
high 7.5

CVE-2026-23666 json

.NET Framework Denial of Service Vulnerability

published 2026-04-14 6 mo ago modified 2026-10-26 13 d ago also EUVD-2026-22363

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.3%
EPSS 1.3% chance of exploitation in 30 days, percentile 71%
public exploits
0
none known

Summary

Improper input validation in .NET Framework allows an unauthorized attacker to deny service over a network.

Patch / fix

  • Microsoft Microsoft .NET Framework 3.5 2.0.50727.8982 & 3.0.30729.8976
  • Microsoft Microsoft .NET Framework 3.5 AND 4.7.2 2.0.50727.9068 & 3.0.30729.9065 & 4.7.4141.0
  • Microsoft Microsoft .NET Framework 3.5 AND 4.8 2.0.50727.9068 & 3.0.30729.9065 & 4.8.4801.0
  • Microsoft Microsoft .NET Framework 3.5 AND 4.8.1 2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0
  • Microsoft Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2 4.8.4801.0
  • Microsoft Microsoft .NET Framework 4.8 4.8.4801.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-23666 updated cvss 7.5

dotnet: .NET Framework: Denial of Service via Race Condition

  • Red Hat Enterprise Linux 8 dotnet, dotnet8.0, dotnet9.0, dotnet10.0, dotnet-host, dotnet-sdk-8.0, +38 more Red Hat Enterprise Linux 9 dotnet8.0, dotnet9.0, dotnet10.0, dotnet-host, dotnet-sdk-8.0, dotnet-sdk-9.0, +37 more Red Hat Enterprise Linux 10 dotnet8.0, dotnet9.0, dotnet10.0
    not affected: component not present
  • Red Hat Hardened Images dotnet8.0, dotnet9.0, dotnet10.0
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

1.33% chance of exploitation in the next 30 days, higher than 71% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Microsoft Microsoft .NET Framework 3.5
  • Microsoft Microsoft .NET Framework 3.5 AND 4.7.2
  • Microsoft Microsoft .NET Framework 3.5 AND 4.8
  • Microsoft Microsoft .NET Framework 3.5 AND 4.8.1
  • Microsoft Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2
  • Microsoft Microsoft .NET Framework 4.8
  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Hardened Images

Classification

Weakness
  • CWE-755 Improper Handling of Exceptional Conditions
  • CWE-366 Race Condition within a Thread

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.